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/cast-imaging/.github/plugin/plugin.json

@@ -0,0 +1,10 @@
+{
+  "name": "cast-imaging",
+  "description": "A comprehensive collection of specialized agents for software analysis, impact assessment, structural quality advisories, and architectural review using CAST Imaging.",
+  "version": "1.0.0",
+  "author": {
+    "name": "Awesome Copilot Community"
+  },
+  "repository": "https://github.com/github/awesome-copilot",
+  "license": "MIT"
+}