feat(plugins): add standalone plugin.json for 4 new community skills

Each skill is now individually installable:
- llm-cost-optimizer
- prompt-governance
- business-investment-advisor
- video-content-strategist

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

engineering/llm-cost-optimizer/.claude-plugin/plugin.json

@@ -0,0 +1,13 @@
+{
+  "name": "llm-cost-optimizer",
+  "description": "Use when you need to reduce LLM API spend, control token usage, route between models by cost/quality, implement prompt caching, or build cost observability for AI features. Triggers: 'my AI costs are ",
+  "version": "2.2.0",
+  "author": {
+    "name": "Alireza Rezvani",
+    "url": "https://alirezarezvani.com"
+  },
+  "homepage": "https://github.com/alirezarezvani/claude-skills/tree/main/engineering/llm-cost-optimizer",
+  "repository": "https://github.com/alirezarezvani/claude-skills",
+  "license": "MIT",
+  "skills": "./"
+}