feat: Add release-please-action for automated releases

## Overview
Integrate [Google's release-please-action](https://github.com/googleapis/release-please-action) to automate the release process for vercel-action.

## Motivation
- Automate version bumping based on conventional commits
- Generate changelogs automatically
- Create GitHub releases with proper tags
- Streamline the release process with release PRs

## Implementation Plan

### 1. Add Release Please Workflow
Create `.github/workflows/release-please.yml`:
```yaml
name: Release Please

on:
push:
branches:
- master

permissions:
contents: write
pull-requests: write

jobs:
release-please:
runs-on: ubuntu-latest
steps:
- uses: googleapis/release-please-action@v4
with:
release-type: node
package-name: vercel-action
```

### 2. Configuration Details
- **Release Type**: `node` (for NPM package with package.json version management)
- **Branch**: `master` (main branch)
- **Version Strategy**: Based on conventional commits
- `fix:` → patch version (41.1.4 → 41.1.5)
- `feat:` → minor version (41.1.4 → 41.2.0)
- `feat!:` or BREAKING CHANGE → major version (41.1.4 → 42.0.0)

### 3. Additional Considerations
- The project already uses conventional commits format
- Ensure `dist/` folder is built and committed during releases
- CHANGELOG.md will be automatically maintained

## Benefits
1. **Automated Version Management**: No manual version bumping needed
2. **Consistent Changelog**: Generated from commit messages
3. **Release PRs**: Review changes before releasing
4. **GitHub Releases**: Automatic creation with proper tags
5. **Semantic Versioning**: Follows SemVer based on commit types

## References
- [release-please-action documentation](https://github.com/googleapis/release-please-action)
- [Conventional Commits](https://www.conventionalcommits.org/)

## Tasks
- [ ] Create release-please workflow file
- [ ] Test with next merge to master
- [ ] Update contributing docs if needed