chore: add 'Stickers and Emojis' as featured space (#2842)

* Mention CLA in CONTRIBUTING.md

Closes: #2146

* add: 'Stickers and Emojis' to config.json

Add #stickers-and-emojis:tastytea.de (space) to config.json

config.json

@@ -11,7 +11,8 @@
       "#space:unredacted.org",
       "#science-space:matrix.org",
       "#libregaming-games:tchncs.de",
-      "#mathematics-on:matrix.org"
+      "#mathematics-on:matrix.org",
+      "#stickers-and-emojis:tastytea.de"
     ],
     "rooms": [
       "#cinny:matrix.org",