fix: serialize metadata extensions

Prism has introduced a few extensions to the meta component version
format, which were not exported as JSON in the launcher. This caused the
`Customize` button on the version page to not write these new properties
to the custom component file.

Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>

launcher/minecraft/MojangVersionFormat.cpp

@@ -306,6 +306,15 @@ void MojangVersionFormat::writeVersionProperties(const VersionFile* in, QJsonObj
         }
         out.insert("downloads", downloadsOut);
     }
+    if(in->compatibleJavaMajors.size())
+    {
+        QJsonArray compatibleJavaMajorsOut;
+        for(auto compatibleJavaMajor : in->compatibleJavaMajors)
+        {
+            compatibleJavaMajorsOut.append(compatibleJavaMajor);
+        }
+        out.insert("compatibleJavaMajors", compatibleJavaMajorsOut);
+    }
 }
 
 QJsonDocument MojangVersionFormat::versionFileToJson(const VersionFilePtr &patch)