Update README.md (#2131)

Fixed formatting of ``package.json``

Author: litetex

README.md

@@ -36,7 +36,7 @@ npm i -S @mongodb-js/compass-aggregations@latest
 ```
 
 And in package.json:
-```json
+```js
 "distributions": {
   "plugin-prefix": "@mongodb-js/compass",
   "default": "compass",