Update README to mention Rhombus support (#142)

Author: Anirban-001

README.md

@@ -28,6 +28,7 @@ Magic Racket **does**
 - Support Racket LSP through [racket-langserver](https://github.com/jeapostrophe/racket-langserver), which brings jump to definition, hover information, formatting, and more
 - Have nearly complete support for every valid Racket syntax: byte strings, regexps, define clauses, vectors... You name it, we have it
 - Support highlighting of all of the standard functions in `#lang racket`
+- Include syntax highlighting and LSP support for Rhombus (`.rhm`) files
 - Turn many little VS Code knobs and switches to provide you the best possible Racket-writing experience
 
 ...but at the same time **doesn't**: