ci: Ensure long changelogs do not crash release pipeline. Use softprops/action-gh-release for release with assets upload included. Trim Discord webhook message.

improv(GUI): DIsplay required Java version correlating to selected Minecraft version. Add getters and setters to allow read & write from addons. Warn if selected Minecraft version has no server available.

fix(VersionMeta): Provide default manifests. Prevents SPC from not starting up properly just because the servers of a modloader aren't accessible.

feat(Scan selected modpack directory & Java 8/17 paths in script variables): After selecting the modpack-directory, Minecraft version, modloader and modloader version are automatically set, if possible. Display required Java version. Allow defining Java 8 and 17 paths for local testing and automatically update SPC_JAVA_SPC.

improv(Java Script Variable Update): Allow disabling of automatic update of SPC_JAVA_SPC-placeholder in script variables

GUI upgrades lets gooooooooooooooo

See merge request !316