Lint for british spelling

Summary:
I hate when I have to comment on a diff and tell somebody to please not use
Her Majesty's Spelling, so I'll let the computer do the shouting.

Mixing two ways of spelling the same thing just isn't fun. I had to
work with an Android library that insisted on spelling it `colour`,
leading to awkward code like `colour: COLORS.BLUE` which is just annoying
and hard to remember.

Reviewed By: lblasa

Differential Revision: D30015807

fbshipit-source-id: 9f913e72617301273dbe12c60b9cdba8cea05537

desktop/.eslintrc.js

@@ -44,6 +44,7 @@ module.exports = {
     'react-hooks',
     'flipper',
     'promise',
+    'communist-spelling',
   ],
   rules: {
     // disable rules from eslint-config-fbjs
@@ -102,6 +103,7 @@ module.exports = {
     'flipper/no-relative-imports-across-packages': [2],
     'flipper/no-electron-remote-imports': [1],
     'flipper/no-console-error-without-context': [1],
+    'communist-spelling/communist-spelling': [1],
 
     // promise rules, see https://github.com/xjamundx/eslint-plugin-promise for details on each of them
     'promise/catch-or-return': 'warn',