Add a pre-commit configuration file

Close #141

Author: NathanLovato

.pre-commit-hooks.yaml

@@ -0,0 +1,6 @@
+- id: gdscript-formatter
+  name: GDScript Formatter
+  description: Format GDScript files with gdscript-formatter
+  entry: gdscript-formatter --safe
+  language: unsupported
+  files: \.gd$

README.md

@@ -79,6 +79,9 @@ It will print the files that need to be formatted.
 
 To see other possible options, run `gdscript-formatter --help`.
 
+
+## Using editorconfig
+
 You can also configure the formatter with an [EditorConfig](https://editorconfig.org/) file at the root of your project. This is a good way to share the same formatting settings with your whole team. The formatter supports the standard keys `indent_style`, `indent_size`, `max_line_length`, `insert_final_newline`, and `trim_trailing_whitespace`, plus custom keys prefixed with `gdscript_formatter_`. See the [GDScript Formatter docs](https://www.gdquest.com/library/gdscript_formatter/) for the complete list. Note that command line flags override `.editorconfig` values.
 
 Use `--quote-style preserve/single/double` to automatically normalize the string quote style. You can also set the style in your `.editorconfig` file using the key `gdscript_formatter_quote_style`. The default value, `preserve`, leaves existing quotes unchanged.
@@ -92,6 +95,24 @@ gdscript_formatter_format_on_save = true
 
 Use this to force everyone in your team to format their GDScript files on save.
 
+
+## Formatting automatically on commit with pre-commit
+
+You can run the formatter automatically before each commit with a version control hook. If your team uses the pre-commit framework, you can add the formatter hook to your project's `.pre-commit-config.yaml` configuration file:
+
+```yaml
+repos:
+  - repo: https://github.com/GDQuest/GDScript-formatter
+    rev: 0.21.0  # use the tag of the version you want to use
+    hooks:
+      - id: gdscript-formatter
+```
+
+See the [formatter documentation](http://gdquest.com/library/gdscript_formatter#formatting-automatically-on-commit) for some more detailed information on this.
+
+
+## Keeping a section of code as-is
+
 To keep a section of code exactly as you wrote it, wrap it between `# fmt: off` and `# fmt: on` comments. This is especially useful when you want to keep values aligned or arranged in a specific way when long data structures:
 
 ```gdscript