Update Readme/Docs on how to setup Java

[Cypressxyx]

Issue

While setting up the java dependency, I was getting

Coverage report not available for filetype java

Soultion

After debugging, I discovered this was because I did not install the neotest dependency which was required for java coverage to work

what was done

• updated readme with how to setup java
• updated nvim doc on what java supports for additional options

test

• verified on personal branch