✨ Add pre-commit hook

[derekrgreene]

Please check if the PR fulfills these requirements:

• The commit message follows our guidelines.
• For bug fixes and features:
  • You tested the changes.

Related issue (if applicable): #141

What kind of change does this PR introduce?

• New feature

Does this PR introduce a breaking change?

• No

New feature or change

What is the current behavior?

There is no .pre-commit-hooks.yaml, so users who want to use gdscript-formatter as a pre-commit hook have to configure it manually.

What is the new behavior?

Users can reference this repo directly in their .pre-commit-config.yaml:

repos:
- repo: https://github.com/GDQuest/GDScript-formatter
    rev: 0.19.0                                                                                                                                                                  
    hooks:                                                                                                                                                                     
    - id: gdscript-formatter                                                                                                                                                     

Other information

Fixes #141