feat: implement list_merge_requests functionality

- Add ListMergeRequestsSchema with comprehensive filtering options
- Implement listMergeRequests function following GitLab API
- Add tool definition and switch case handler
- Include in readOnlyTools array
- Update README.md with new tool documentation

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@zereight/mcp-gitlab",
-  "version": "1.0.38",
+  "version": "1.0.46",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@zereight/mcp-gitlab",
-      "version": "1.0.38",
+      "version": "1.0.46",
       "license": "MIT",
       "dependencies": {
         "@modelcontextprotocol/sdk": "1.8.0",