Add automated workflow for category JSON updates and documentation

[pphatdev]

Description

This PR introduces a fully automated GitHub Actions workflow to manage the root category JSON files (brands.json, regular.json), removing the need for manual updates from contributors. It also significantly improves the repository's documentation and issue management structure.

Key Changes:

• Automated JSON Compilation: Added a new GitHub Actions workflow (update-category.yml) that triggers on PRs, pushes to main/master, and release tags. It automatically scans the brands/ and regular/ directories and compiles the root index JSON files.
• TypeScript Scripting: Recreated the update script in TypeScript (update-category.ts) with strict typing, bundled efficiently via tsup. To keep the root clean, all script configuration (package.json, tsconfig.json) was moved into the .github/scripts/ directory.
• Documentation Updates: Completely overhauled CONTRIBUTING.md and README.md to instruct users to just drop their .json files into the category folders, removing outdated manual SVG and index instructions.
• PR & Issue Templates: Added a strict .github/PULL_REQUEST_TEMPLATE.md to enforce the new workflow rules via a checklist. Additionally, created GitHub Issue templates for Icon Requests, Bug Reports, and Feature Requests to better organize community feedback.

Checklist

Please make sure your Pull Request follows these guidelines:

• I have placed my new or updated .json icon file in the correct category directory (brands/ or regular/).
• My file uses a lowercase name with hyphens for spaces (e.g., my-brand.json).
• I have NOT manually edited the root brands.json or regular.json files (our GitHub Actions workflow will handle this automatically!).
• My JSON configuration is valid and follows the schema.
• I have read the CONTRIBUTING.md guide.

Additional Notes

Tested locally by running the build script in .github/scripts and everything successfully updates brands.json and regular.json.