Add plugins for all collections

Generate plugin directories for 36 collections not previously represented:
- awesome-copilot, cast-imaging, clojure-interactive-programming, copilot-sdk
- csharp-dotnet-development, csharp-mcp-development, database-data-management
- dataverse-sdk-for-python, devops-oncall, edge-ai-tasks, frontend-web-dev
- go-mcp-development, java-development, java-mcp-development, kotlin-mcp-development
- mcp-m365-copilot, openapi-to-application-* (5 variants), partners
- pcf-development, php-mcp-development, power-apps-code-apps, power-bi-development
- power-platform-mcp-connector-development, python-mcp-development
- ruby-mcp-development, rust-mcp-development, security-best-practices
- structured-autonomy, swift-mcp-development, technical-spike
- typescript-mcp-development, typespec-m365-copilot

Each plugin includes:
- .github/plugin/plugin.json with metadata
- README.md with installation instructions
- Symlinks to canonical agents, commands, and skills

Updated marketplace.json to include all 40 plugins.

plugins/csharp-dotnet-development/README.md

@@ -0,0 +1,43 @@
+# C# .NET Development Plugin
+
+Essential prompts, instructions, and chat modes for C# and .NET development including testing, documentation, and best practices.
+
+## Installation
+
+```bash
+# Using Copilot CLI
+copilot plugin install github/awesome-copilot/plugins/csharp-dotnet-development
+```
+
+## What's Included
+
+### Commands (Slash Commands)
+
+| Command | Description |
+|---------|-------------|
+| `/csharp-dotnet-development:csharp-async` | Csharp Async |
+| `/csharp-dotnet-development:aspnet-minimal-api-openapi` | Aspnet Minimal Api Openapi |
+| `/csharp-dotnet-development:csharp-xunit` | Csharp Xunit |
+| `/csharp-dotnet-development:dotnet-best-practices` | Dotnet Best Practices |
+| `/csharp-dotnet-development:dotnet-upgrade` | Dotnet Upgrade |
+
+### Agents
+
+| Agent | Description |
+|-------|-------------|
+| `expert-dotnet-software-engineer` | Expert Dotnet Software Engineer |
+
+### Instructions
+
+| Instruction | Description |
+|-------------|-------------|
+| `csharp` | Csharp |
+| `dotnet-architecture-good-practices` | Dotnet Architecture Good Practices |
+
+## Source
+
+This plugin is part of [Awesome Copilot](https://github.com/github/awesome-copilot), a community-driven collection of GitHub Copilot extensions.
+
+## License
+
+MIT