Add Sia's Mastodon link (#3802)

* Update contributors.json with Mastodon link and 2024 contributor (Sia)

* Update contributors.json

* Update contributors.json

---------

Co-authored-by: Barry Pollard <barrypollard@google.com>

Author: siakaramalegos

src/config/contributors.json

@@ -3673,6 +3673,7 @@
     "avatar_url": "4777393",
     "github": "siakaramalegos",
     "linkedin": "karamalegos",
+    "mastodon": "https://front-end.social/@sia",
     "name": "Sia Karamalegos",
     "teams": {
       "2021": [
@@ -3685,7 +3686,6 @@
         "leads"
       ]
     },
-    "twitter": "TheGreenGreek",
     "website": "https://sia.codes"
   },
   "simonhearne": {