DOC: Add gallery example to show text formatting (#3987)

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

Author: yvonnefroehlich

examples/gallery/embellishments/text_formatting.py

@@ -0,0 +1,41 @@
+"""
+Text formatting
+===============
+
+There are various options for formatting text contained in a plot, e.g., text added via
+:meth:`pygmt.Figure.text`, the plot title, labels of colorbars as well as Cartesian
+axes, and legend entries. It's also possible to change the font as well as its color
+and size only for specific characters of a longer text. The supported fonts are listed
+at :doc:`Supported Fonts </techref/fonts>`. For an complete overview see
+:doc:`Text Formatting </techref/text_formatting>`.
+"""
+
+# %%
+import pygmt
+
+fig = pygmt.Figure()
+fig.basemap(region=[-1, 1, -4, 4], projection="X4c/5c", frame=0)
+
+# Change font color for specific letters of the word "PyGMT":
+# blue for "P", yellow for "y", and red for "GMT"
+fig.text(x=0, y=3, text="@;63/124/173;P@;;@;255/212/59;y@;;@;238/86/52;GMT@;;")
+
+# Change font size and style for one single character, respectively
+fig.text(x=0, y=2, text="te@:15:x@::t     tex@%Courier-Oblique%t@%%")
+
+# Use superscript
+fig.text(x=0, y=1, text="E = mc@+2@+")
+
+# Use subscripts and Greek letters
+fig.text(x=0, y=0, text="@~s@~@-ij@- = c@-ijkl@- @~e@~@-kl@-")
+
+# Combine two characters above each other
+fig.text(x=0, y=-1, text="@!_~")
+
+# Underline the text
+fig.text(x=0, y=-2, text="This is @_underlined@_ text")
+
+# Use small caps
+fig.text(x=0, y=-3, text="T@#ext@# in S@#mall@# C@#aps@#")
+
+fig.show()