Add code style formatting

[LeafHacker]

Spotless is a cool code formatting util that can be easily integrated into build.gradle and configured for custom code formatting of different file types.

This will be usable as gradle tasks to check and fix formatting. I may also look into adding git hooks so the tasks are run when making a git commit.

[LeafHacker]

~~I may consider using checkstyle instead of spotless after some more investigation~~ looks like checkstyle is code analysis not formatting