Mod Generator outputs outdated Gradle & Java versions

[Hex4dec]

it.options.release should be 21, and ``distributionUrl` should point to the 8.8 version instead of 8.7. Also sourceCompatibility, targetCompatibility, and Mixin Java version is wrong.

Also, QSL fails to be imported.

[UpcraftLP]

Feel free to make a PR to update the template mod to MC 1.21.

As for the QSL import, that was an oversight when publishing QFAPI, you can work around it for now by manually adding a dependency on qsl, or wait until the next QFAPI release to fix it.