Add twitter icon

CHANGELOG.md

@@ -54,6 +54,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   - `thumbs-down`
   - `thumbs-up`
   - `triangle`
+  - `twitter`
   - `user-minus`
   - `user-plus`
   - `video-off`

icons-manifest.json

@@ -34,6 +34,7 @@
   "facebook",
   "instagram",
   "pocket",
+  "twitter",
   "at-sign",
   "hash",
   "phone",

icons/twitter.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#000" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+  <path d="M23,3a10.9,10.9,0,0,1-3.14,1.53A4.48,4.48,0,0,0,12,7.5c0,.17,0,.83,0,1C7,8.5,4,5.5,2,3,2,3-2,13,8,17H8a11.64,11.64,0,0,1-7,2c9,5,20,0,20-11.5a4.5,4.5,0,0,0-.08-.83A7.72,7.72,0,0,0,23,3Z"/>
+</svg>
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