chore: fix editorconfig

- all JS/JSON/yaml are already using spaces, so having indent-style as tab just confuses the editor.
- only the README.md is using tabs for whitespace, for which a new rule is added

Author: Kumar Harsh

.editorconfig

@@ -5,10 +5,14 @@ root = true
 [*]
 end_of_line = lf
 charset = utf-8
-trim_trailing_whitespace = false
+trim_trailing_whitespace = true
 insert_final_newline = true
-indent_style = tab
+indent_style = space
 
 [*.json]
 indent_style = space
 indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+indent_style = tab