Feature/add slack channel (#363)

* Add Slack channel

* Update changelog

apps/client/src/app/pages/about/about-page.html

@@ -32,7 +32,12 @@
           </p>
           <p>
             If you encounter a bug or would like to suggest an improvement or a
-            new feature, please tweet to
+            new feature, please join the Ghostfolio
+            <a
+              href="https://join.slack.com/t/ghostfolio/shared_invite/zt-vsaan64h-F_I0fEo5M0P88lP9ibCxFg"
+              title="Join the Ghostfolio Slack channel"
+              >Slack channel</a
+            >, tweet to
             <a
               href="https://twitter.com/ghostfolio_"
               title="Tweet to Ghostfolio on Twitter"
@@ -65,6 +70,14 @@
             >
               <ion-icon name="mail" size="large"></ion-icon>
             </a>
+            <a
+              class="mx-2"
+              href="https://join.slack.com/t/ghostfolio/shared_invite/zt-vsaan64h-F_I0fEo5M0P88lP9ibCxFg"
+              mat-icon-button
+              title="Join the Ghostfolio Slack channel"
+            >
+              <ion-icon name="logo-slack" size="large"></ion-icon>
+            </a>
             <a
               class="mx-2"
               href="https://github.com/ghostfolio/ghostfolio"