docs: add RFC commands to README and bump projman version

- Add 5 RFC commands to projman Commands line in README.md
- Bump projman version 3.3.0 → 3.4.0 in marketplace.json

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -11,7 +11,7 @@
   "plugins": [
     {
       "name": "projman",
-      "version": "3.3.0",
+      "version": "3.4.0",
       "description": "Sprint planning and project management with Gitea integration",
       "source": "./plugins/projman",
       "author": {