Add link to RSS feed to the profile (#234)

Today I learned that akkoma and mastodon (and potentially other activitypub services) offer RSS/Atom feeds for user profiles at `[user profile url].rss`. This PR adds a direct link to the feed because I haven’t seen anything link to the feed on either mastodon-fe or pleroma-fe

Co-authored-by: Charlotte 🦝 Delenk <lotte@chir.rs>
Reviewed-on: https://akkoma.dev/AkkomaGang/pleroma-fe/pulls/234
Co-authored-by: darkkirb <lotte@chir.rs>
Co-committed-by: darkkirb <lotte@chir.rs>

src/components/user_card/user_card.vue

@@ -67,6 +67,17 @@
                   icon="external-link-alt"
                 />
               </a>
+              <a
+                v-if="isOtherUser"
+                :href="user.statusnet_profile_url + '.rss'"
+                target="_blank"
+                class="button-unstyled external-link-button"
+              >
+                <FAIcon
+                  class="icon"
+                  icon="rss"
+                />
+              </a>
               <AccountActions
                 v-if="isOtherUser && loggedIn"
                 :user="user"