chore: add repo essentials and GitHub templates

- Add MIT LICENSE file
- Add CONTRIBUTING.md with skill creation guide
- Add AGENTS.md and CLAUDE.md for AI agent guidelines
- Add issue template for skill requests
- Add PR templates for new skills, updates, and docs
- Update README with links to contributing guide and license

CONTRIBUTING.md

@@ -0,0 +1,91 @@
+# Contributing
+
+Thanks for your interest in contributing to Marketing Skills! This guide will help you add new skills or improve existing ones.
+
+## Requesting a Skill
+
+You can also suggest new skills by [opening a skill request](https://github.com/coreyhaines31/marketingskills/issues/new?template=skill-request.yml).
+
+## Adding a New Skill
+
+### 1. Create the skill directory
+
+```bash
+mkdir -p skills/your-skill-name
+```
+
+### 2. Create the SKILL.md file
+
+Every skill needs a `SKILL.md` file with YAML frontmatter:
+
+```yaml
+---
+name: your-skill-name
+description: When to use this skill. Include trigger phrases and keywords that help agents identify relevant tasks.
+license: MIT
+metadata:
+  author: "[Your Name](https://your-website.com)"
+  version: "1.0.0"
+---
+
+# Your Skill Name
+
+Instructions for the agent go here...
+```
+
+### 3. Follow the naming conventions
+
+- **Directory name**: lowercase, hyphens only (e.g., `email-sequence`)
+- **Name field**: must match directory name exactly
+- **Description**: 1-1024 characters, include trigger phrases
+
+### 4. Structure your skill
+
+```
+skills/your-skill-name/
+├── SKILL.md           # Required - main instructions
+├── references/        # Optional - additional documentation
+│   └── guide.md
+├── scripts/           # Optional - executable code
+│   └── helper.py
+└── assets/            # Optional - templates, images, data
+    └── template.json
+```
+
+### 5. Write effective instructions
+
+- Keep `SKILL.md` under 500 lines
+- Move detailed reference material to `references/`
+- Include step-by-step instructions
+- Add examples of inputs and outputs
+- Cover common edge cases
+
+## Improving Existing Skills
+
+1. Read the existing skill thoroughly
+2. Test your changes locally
+3. Keep changes focused and minimal
+4. Update the version in metadata if making significant changes
+
+## Submitting Your Contribution
+
+1. Fork the repository
+2. Create a feature branch (`git checkout -b feat/new-skill-name`)
+3. Make your changes
+4. Test locally with an AI agent
+5. Submit a pull request using the appropriate template:
+   - [New Skill](?template=new-skill.md)
+   - [Skill Update](?template=skill-update.md)
+   - [Documentation](?template=documentation.md)
+
+## Skill Quality Checklist
+
+- [ ] `name` matches directory name
+- [ ] `description` clearly explains when to use the skill
+- [ ] Instructions are clear and actionable
+- [ ] No sensitive data or credentials
+- [ ] Follows existing skill patterns in the repo
+
+## Questions?
+
+Open an issue if you have questions or need help with your contribution.