Add a .pre-commit-hooks.yaml and add it to contributing guideline

[m21-cerutti]

Which demo project is affected:
All possibly to clean.

Description:
Could be interesting to add a pre commit hook to clean commits before pull requests and add it to recommended guidelines.
Would make smoother I think the review process.

Resources:
https://pre-commit.com/
https://github.com/Scony/godot-gdscript-toolkit/blob/master/.pre-commit-hooks.yaml

For context I got the idea with this review
#1085

[aaronfranke]

This is a good idea, yeah. We already have this for the engine repo, having pre-commit here too would be nice. At a minimum it could perform the same basic checks as CI, at best it could perform more formatting.

[m21-cerutti]

I tried to have a first try with

default_install_hook_types: [pre-commit]
repos:

# Linters
-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
    -   id: check-added-large-files
    -   id: check-case-conflict
    -   id: check-merge-conflict
    -   id: end-of-file-fixer
    -   id: trailing-whitespace
    -   id: check-json
    -   id: check-symlinks

-   repo: https://github.com/Scony/godot-gdscript-toolkit
    rev: 4.2.2
    hooks:
        - id: gdlint
          exclude: .*screenshots/
        - id: gdformat
          exclude: .*screenshots/

but seems it would need more setup

[AThousandShips]

Note that, as seen in #1085, the proposed linter does not correctly follow the GDScript style guide, so it'd have to be improved to properly handle that before it can be used here