Add badges for supported platforms.

Author: netomi

README.md

@@ -3,6 +3,8 @@ A sudoku solver / generator.
 ============================
 
 ![Build status](https://github.com/netomi/sudoku-solver/workflows/build-status/badge.svg)
+![badge][badge-jvm]
+![badge][badge-js]
 
 This repository contains a multiplatform library written in
 Kotlin to solve and generate sudoku puzzles.