Add webp image processing

composer.json

@@ -19,6 +19,7 @@
     "kigkonsult/icalcreator": "^2.29",
     "league/csv": "^9.2",
     "league/period": "^4.9",
+    "plan2net/webp": "^4.1",
     "ssch/typo3-encore": "^3.0",
     "symfony/http-client": "^4.3",
     "symfony/options-resolver": "^4.2",