feat: add changelog to mod providers

The Modrinth changelog is fairly straight-forward, as it's given to us
directly with the API call we already did. Flame, on the other hand,
requires us to do another call to get the changelog, so it can introduce
quite a heavy performance impact. This way, we make it optional to get
such changelog.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/modplatform/flame/FlameModIndex.h

@@ -17,6 +17,6 @@ void loadIndexedPackVersions(ModPlatform::IndexedPack& pack,
                              QJsonArray& arr,
                              const shared_qobject_ptr<QNetworkAccessManager>& network,
                              BaseInstance* inst);
-auto loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedVersion;
+auto loadIndexedPackVersion(QJsonObject& obj, bool load_changelog = false) -> ModPlatform::IndexedVersion;
 
 }  // namespace FlameMod