Update dependency fast-xml-parser to v4 [SECURITY]

Author: renovate[bot]

package-lock.json

@@ -18,7 +18,7 @@
         "eslint": "^6.8.0",
         "express": "^4.17.3",
         "express-github-webhook": "^1.0.6",
-        "fast-xml-parser": "^3.21.1",
+        "fast-xml-parser": "^4.0.0",
         "ffmpeg": "0.0.4",
         "ffmpeg-static": "^3.0.0",
         "fluent-ffmpeg": "^2.1.2",