README: add links to cuelang.org guides

Signed-off-by: Jonathan Matthews <github@hello.jonathanmatthews.com>
Change-Id: I14c3a3864cb78bd53c59f3b1ecf2f9d79c22b0c4
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue-api-java/+/1202152
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

Author: jpluscplusm

README.md

@@ -15,7 +15,8 @@ you might need to change that.
 
 ## Using
 
-TODO.
+- [Getting started using CUE in Java](https://cuelang.org/docs/tutorial/get-started-cue-java/) on cuelang.org
+- [Other Java+CUE guides](https://cuelang.org/search/?q=tag:%22java%20api%22) on cuelang.org
 
 ## Known Limitations