1.9.10.5 Support Release, with Gradle 6.3

This release makes some internal changes to gdx-liftoff to hopefully address issues with gdx-tools and LWJGL3 conflicting, updates Gradle to 6.3 (which should allow Java 14 to be used; it could already be selected), and uses libGDX 1.9.10 both for user projects by default and for its own UI. This release may be less compatible with high-DPI screens because it uses LWJGL2 to show its UI instead of LWJGL3, but this should allow the texture packer to work from Gradle scripts.