chore(pr-template): Add PR template for contributing new templates

[aRustyDev]

Summary

Adds a dedicated PR template for contributing new templates to the repository. This template covers PR templates, issue templates, mustache templates, and other template types.

Template Type

• PR template (.github/PULL_REQUEST_TEMPLATE/)

Templates Affected

File	Action	Purpose
.github/PULL_REQUEST_TEMPLATE/templates.md	Added	PR template for template contributions

Related Issues

Checklist

General

• Template follows repository naming conventions
• Template includes clear placeholder text/comments for users
• Template is placed in the correct directory

For PR/Issue Templates

• Template includes all required sections
• Checkboxes and options are relevant to the template's purpose

Template Preview

Key sections include:

• Template Type - Checkboxes for PR, Issue, Mustache, or other template types
• Templates Affected - Table format for listing files with action and purpose
• Checklist - Separated into General, PR/Issue-specific, and Mustache/Code-specific sections
• Template Preview - For describing or demonstrating template output
• Testing - How the template was validated

Testing

Template file created following existing PR template conventions.

Additional Context

This completes the PR template suite:

• mcp-server-default.md - Default for MCP server changes
• wiki-update.md - For Wiki documentation updates
• templates.md - For contributing new templates (this PR)