Document RBS type signatures for contributors (#1998)

## Summary
Add comprehensive documentation about RBS type signatures to help
contributors understand and use type checking.

## Changes
- Created `docs/contributor-info/rbs-type-signatures.md` with detailed
RBS documentation
- Added reference to RBS docs in CONTRIBUTING.md
- Removed previous top-level README section (per PR feedback)

## Documentation Includes
- Benefits of RBS type signatures (better autocomplete, early error
detection, improved documentation, refactoring safety)
- IDE support information (Steep, Solargraph, RubyMine, VS Code)
- Usage instructions for validation and listing type files
- File structure and location information
- Contributing guidelines for adding new signatures
- Compatibility requirements and resources

## Context
React on Rails includes comprehensive RBS type signatures (added in PR
#1945), but this feature wasn't documented for contributors. This
documentation is now properly positioned in the contributor-info
directory.

## Testing
- Verified formatting with Prettier (all checks pass)
- Confirmed all pre-commit hooks pass
- Verified sig/README.md exists and contains detailed RBS documentation
- Confirmed rake tasks exist (rbs:validate, rbs:list)

Fixes #1953

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: justin808

CONTRIBUTING.md

@@ -14,6 +14,7 @@ During this transition:
 
 - [docs/contributor-info/Releasing](./docs/contributor-info/releasing.md) for instructions on releasing.
 - [docs/contributor-info/pull-requests](./docs/contributor-info/pull-requests.md)
+- [docs/contributor-info/rbs-type-signatures](./docs/contributor-info/rbs-type-signatures.md) for information on RBS type signatures
 - See other docs in [docs/contributor-info](./docs/contributor-info)
 
 ## Prerequisites

docs/contributor-info/rbs-type-signatures.md

@@ -0,0 +1,83 @@
+# RBS Type Signatures
+
+React on Rails includes [RBS](https://github.com/ruby/rbs) type signatures for improved type safety and IDE support.
+
+## Benefits
+
+- **Better autocomplete** in supported IDEs
+- **Early detection of type errors** during development
+- **Improved code documentation** through types
+- **Enhanced refactoring safety** with type-aware tools
+
+## IDE Support
+
+RBS signatures work with:
+
+- [Steep](https://github.com/soutaro/steep) - Static type checker for Ruby
+- [Solargraph](https://solargraph.org/) - Ruby language server with RBS support
+- RubyMine - Built-in RBS support
+- VS Code - Via Ruby LSP extensions
+
+## Usage
+
+### Validation
+
+To validate type signatures:
+
+```bash
+bundle exec rake rbs:validate
+```
+
+Or directly using the RBS CLI:
+
+```bash
+bundle exec rbs -I sig validate
+```
+
+### Listing Type Files
+
+To see all available RBS type signature files:
+
+```bash
+bundle exec rake rbs:list
+```
+
+## Location
+
+Type signatures are located in the `sig/` directory, organized to mirror the `lib/` directory structure:
+
+```
+sig/
+├── react_on_rails.rbs              # Main module and core classes
+├── react_on_rails/
+│   ├── configuration.rbs           # Configuration class types
+│   ├── helper.rbs                  # View helper method signatures
+│   ├── server_rendering_pool.rbs   # Server rendering types
+│   ├── utils.rbs                   # Utility method signatures
+│   └── ...                         # And more
+```
+
+For more details, see [sig/README.md](../../sig/README.md).
+
+## Contributing
+
+When adding new public methods or classes to the gem, please also add corresponding RBS signatures. This helps maintain type safety and improves the development experience for all users.
+
+### Adding New Signatures
+
+1. Create or update the appropriate `.rbs` file in the `sig/` directory
+2. Follow the existing structure and naming conventions
+3. Run `bundle exec rake rbs:validate` to verify your changes
+4. Include the RBS updates in your pull request
+
+## Compatibility
+
+- Ruby >= 3.0 (RBS is included in Ruby 3.0+)
+- RBS gem >= 2.0
+
+## Resources
+
+- [RBS Documentation](https://github.com/ruby/rbs)
+- [RBS Syntax Guide](https://github.com/ruby/rbs/blob/master/docs/syntax.md)
+- [Steep Type Checker](https://github.com/soutaro/steep)
+- [Solargraph Language Server](https://solargraph.org/)