Add style guide

[ohno]

First, discuss which style is preferred. Add style guide to .JuliaFormatter.toml.

[ohno]

style	URL
YAS	https://domluna.github.io/JuliaFormatter.jl/dev/yas_style/
Blue	https://domluna.github.io/JuliaFormatter.jl/dev/blue_style/
SciML	https://domluna.github.io/JuliaFormatter.jl/dev/sciml_style/

comparison:

always_for_in = true
always_for_in = true
always_for_in = true

always_use_return = true
always_use_return = false
always_use_return = false

import_to_using = true
import_to_using = true
import_to_using = false

join_lines_based_on_source = true
join_lines_based_on_source = false
join_lines_based_on_source = true

pipe_to_function_call = true
pipe_to_function_call = true
pipe_to_function_call = false

remove_extra_newlines = true
remove_extra_newlines = true
remove_extra_newlines = true

separate_kwargs_with_semicolon = true
separate_kwargs_with_semicolon = true
separate_kwargs_with_semicolon = false

short_to_long_function_def = true
short_to_long_function_def = true
short_to_long_function_def = true

whitespace_in_kwargs = false
whitespace_in_kwargs = false
whitespace_in_kwargs = true

whitespace_ops_in_indices = true
whitespace_ops_in_indices = true
whitespace_ops_in_indices = true

yas_style_nesting = false
yas_style_nesting = false
yas_style_nesting = false

annotate_untyped_fields_with_any = true
annotate_untyped_fields_with_any = false
annotate_untyped_fields_with_any = true

conditional_to_if = false
conditional_to_if = true
conditional_to_if = false

indent_submodule = false
indent_submodule = true
indent_submodule = false

disallow_single_arg_nesting = false
disallow_single_arg_nesting = false
disallow_single_arg_nesting = true

normalize_line_endings = "auto"
normalize_line_endings = "auto"
normalize_line_endings = "unix"

trailing_comma = true
trailing_comma = true
trailing_comma = false

whitespace_typedefs = false
whitespace_typedefs = false
whitespace_typedefs = true

We need to add https://github.com/fredrikekre/Runic.jl.

[ohno]

Basically, I will follow the majority rule of style guides but I have some minority opinions. This is the best style for me:

# https://domluna.github.io/JuliaFormatter.jl/stable/#Formatting-Options
indent                           = 2     # minority. 4 is just a feeling but 2 is necessary in web engineering.
margin                           = 10000 # minority. limit is remnant of punch card era.
always_for_in                    = true
whitespace_typedefs              = false
whitespace_ops_in_indices        = true
remove_extra_newlines            = true
import_to_using                  = false # minority. due to different results.
pipe_to_function_call            = true
short_to_long_function_def       = false # minority. due to no limit of margin.
force_long_function_def          = false
long_to_short_function_def       = false
always_use_return                = false
whitespace_in_kwargs             = true  # minority. false is better for a single line but true is better for multiple lines.
annotate_untyped_fields_with_any = true
format_docstrings                = false
align_assignment                 = true
align_struct_field               = true
align_conditional                = true
align_pair_arrow                 = true
align_matrix                     = true
conditional_to_if                = false
normalize_line_endings           = "auto"
trailing_comma                   = true
trailing_zero                    = false
join_lines_based_on_source       = true
indent_submodule                 = false
separate_kwargs_with_semicolon   = true
surround_whereop_typeparameters  = true
for_in_replacement               = "∈"
variable_call_indent             = []
yas_style_nesting                = false
short_circuit_to_if              = false
disallow_single_arg_nesting      = false
overwrite                        = true
verbose                          = false
format_markdown                  = false

[ohno]

I had better follow the standard 4-space indentation rather than my preference:

# https://domluna.github.io/JuliaFormatter.jl/stable/#Formatting-Options
indent                           = 4
margin                           = 10000 # minority. VSCode manages it.
always_for_in                    = true
whitespace_typedefs              = false
whitespace_ops_in_indices        = true
remove_extra_newlines            = true
import_to_using                  = false # minority. due to different results.
pipe_to_function_call            = true
short_to_long_function_def       = false # minority. due to no limit of margin.
force_long_function_def          = false
long_to_short_function_def       = false
always_use_return                = false
whitespace_in_kwargs             = true  # minority. false is better for a single line but true is better for multiple lines.
annotate_untyped_fields_with_any = true
format_docstrings                = false
align_assignment                 = true
align_struct_field               = true
align_conditional                = true
align_pair_arrow                 = true
align_matrix                     = true
conditional_to_if                = false
normalize_line_endings           = "auto"
trailing_comma                   = true
trailing_zero                    = false
join_lines_based_on_source       = true
indent_submodule                 = false
separate_kwargs_with_semicolon   = true
surround_whereop_typeparameters  = true
for_in_replacement               = "∈"
variable_call_indent             = []
yas_style_nesting                = false
short_circuit_to_if              = false
disallow_single_arg_nesting      = false
overwrite                        = true
verbose                          = false
format_markdown                  = false

There is not a strong consensus on the length of a line.

[ohno]

We should install Runic.jl.