feat(cd): add Matrix notification on deploy failure

Sends a message to a Matrix room when a deploy fails, including
the failing services, commit, deployer, and a link to the logs.

Requires two GitHub Actions secrets:
- DEPLOY_NOTIFY_ROOM_ID: Matrix room ID
- DEPLOY_NOTIFY_BOT_TOKEN: Matrix bot access token

Skips silently if secrets are not configured.

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

games/whopixels/package.json

@@ -0,0 +1,6 @@
+{
+	"dependencies": {
+		"dotenv": "^16.4.7",
+		"node-fetch": "^2.7.0"
+	}
+}