Migrate pcf-development from empty plugin to skill

The pcf-development plugin had no agents, skills, or commands
referenced - just an empty shell. Convert it to a proper skill
with comprehensive PCF development guidance.

Also resolve merge conflict in CONTRIBUTING.md.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

plugins/pcf-development/.github/plugin/plugin.json

@@ -1,17 +0,0 @@
-{
-  "name": "pcf-development",
-  "description": "Complete toolkit for developing custom code components using Power Apps Component Framework for model-driven and canvas apps",
-  "version": "1.0.0",
-  "author": {
-    "name": "Awesome Copilot Community"
-  },
-  "repository": "https://github.com/github/awesome-copilot",
-  "license": "MIT",
-  "keywords": [
-    "power-apps",
-    "pcf",
-    "component-framework",
-    "typescript",
-    "power-platform"
-  ]
-}

plugins/pcf-development/README.md

@@ -1,20 +0,0 @@
-# Power Apps Component Framework (PCF) Development Plugin
-
-Complete toolkit for developing custom code components using Power Apps Component Framework for model-driven and canvas apps
-
-## Installation
-
-```bash
-# Using Copilot CLI
-copilot plugin install pcf-development@awesome-copilot
-```
-
-## What's Included
-
-## Source
-
-This plugin is part of [Awesome Copilot](https://github.com/github/awesome-copilot), a community-driven collection of GitHub Copilot extensions.
-
-## License
-
-MIT