Support launching net.minecraft.client.Minecraft in old versions

[Flamarine]

trafficstars

Supporting launching net.minecraft.client.Minecraft might help improve the compatibility with some base edit mods for legacy versions that don't use applets. For instance, Better than Adventure (This mod currently crashes on startup because Quilt Loader only tries to launch net.minecraft.client.MinecraftApplet).

[Oliver-makes-code]

This also causes an issue where trying to close the game causes the window to freeze instead of closing