Create release notes for v0.19.0 pre-release

Author: LadyKerr

RELEASE_NOTES.md

@@ -0,0 +1,19 @@
+# GitHub MCP Server v0.19.0
+
+## 📚 Documentation
+
+- **Improved GHES/GHEC visibility in README** - Restructured documentation to better highlight GitHub Enterprise Server and GitHub Enterprise Cloud configuration, including fixes to example URLs that were previously causing confusion ([#1210](https://github.com/github/github-mcp-server/pull/1210)) - @tonytrg
+
+## ✨ New Features
+
+- **Flexible toolset configuration** - Added option to ignore unknown toolsets instead of raising errors, providing more flexibility in configuration scenarios ([#1202](https://github.com/github/github-mcp-server/pull/1202)) - @omgitsads
+
+## 🔧 Maintenance & Refactoring
+
+- **Consolidated pull request review tools** - Unified multiple PR review tools (`create_and_submit_pull_request_review`, `create_pending_pull_request_review`, `submit_pending_pull_request_review`, `delete_pending_pull_request_review`) into a single `pull_request_review_write` tool with a `method` parameter (`create`, `submit_pending`, `delete_pending`). Validated against curated datasets with no regressions across models ([#1192](https://github.com/github/github-mcp-server/pull/1192)) - @almaleksia
+
+- **Simplified Registry release pipeline** - Streamlined the registry publication workflow by using version tag triggers instead of repository dispatch, removing the need for elevated permissions. Added a 5-minute wait mechanism to ensure Docker image availability before MCP Registry publication ([#1204](https://github.com/github/github-mcp-server/pull/1204)) - @MattBabbage
+
+## 🔒 Security
+
+- **Reduced workflow permissions** - Registry release pipeline no longer requires elevated `actions:write` permissions, minimizing security risk ([#1204](https://github.com/github/github-mcp-server/pull/1204)) - @MattBabbage