Update docs from rizinorg/cutter

Original Commit:
a47d3a1022c9a081cf05acfafb3fbdd352b9e072 Add missing Mattermost link

Author: actions-user

docs/_sources/index.rst.txt

@@ -35,6 +35,7 @@ Need help?
 
 You can contact the *Cutter* developers and community on:
 
+-  Mattermost: https://im.rizin.re
 -  Telegram: https://t.me/cutter_re
 -  #cutter on https://web.libera.chat
 -  Twitter: https://twitter.com/cutter_re

docs/index.html

@@ -61,6 +61,7 @@ <h2>Building from Sources<a class="headerlink" href="#building-from-sources" tit
 <h2>Need help?<a class="headerlink" href="#need-help" title="Link to this heading">¶</a></h2>
 <p>You can contact the <em>Cutter</em> developers and community on:</p>
 <ul class="simple">
+<li><p>Mattermost: <a class="reference external" href="https://im.rizin.re">https://im.rizin.re</a></p></li>
 <li><p>Telegram: <a class="reference external" href="https://t.me/cutter_re">https://t.me/cutter_re</a></p></li>
 <li><p>#cutter on <a class="reference external" href="https://web.libera.chat">https://web.libera.chat</a></p></li>
 <li><p>Twitter: <a class="reference external" href="https://twitter.com/cutter_re">https://twitter.com/cutter_re</a></p></li>