Bug 1833949 - Port bug 1826062: Prettier config changes for v2.0.5. r=leftmostcat

arrowParens now defaults to "always". Upstream is setting it to "avoid". This is
to keep calendar code from reformatting arrow functions.

Differential Revision: https://phabricator.services.mozilla.com/D178536

--HG--
extra : amend_source : a1f44df1a2639dc95a8d0cdb4d502425ab653516

calendar/.prettierrc

@@ -1,4 +1,6 @@
 {
+  "arrowParens": "avoid",
+  "endOfLine": "lf",
   "printWidth": 100,
   "tabWidth": 2,
   "trailingComma": "es5"