Link to mobile apps page (#8278)

Fix #8269

app/javascript/mastodon/features/getting_started/index.js

@@ -139,6 +139,7 @@ export default class GettingStarted extends ImmutablePureComponent {
             {multiColumn && <li><Link to='/keyboard-shortcuts'><FormattedMessage id='navigation_bar.keyboard_shortcuts' defaultMessage='Hotkeys' /></Link> · </li>}
             <li><a href='/auth/edit'><FormattedMessage id='getting_started.security' defaultMessage='Security' /></a> · </li>
             <li><a href='/about/more' target='_blank'><FormattedMessage id='navigation_bar.info' defaultMessage='About this instance' /></a> · </li>
+            <li><a href='https://joinmastodon.org/apps' target='_blank'><FormattedMessage id='navigation_bar.apps' defaultMessage='Mobile apps' /></a> · </li>
             <li><a href='/terms' target='_blank'><FormattedMessage id='getting_started.terms' defaultMessage='Terms of service' /></a> · </li>
             <li><a href='/settings/applications' target='_blank'><FormattedMessage id='getting_started.developers' defaultMessage='Developers' /></a> · </li>
             <li><a href='https://github.com/tootsuite/documentation#documentation' target='_blank'><FormattedMessage id='getting_started.documentation' defaultMessage='Documentation' /></a> · </li>

app/views/layouts/public.html.haml

@@ -45,6 +45,6 @@
             %h4= t 'footer.more'
             %ul
               %li= link_to t('about.source_code'), Mastodon::Version.source_url
-              %li= link_to 'joinmastodon.org', 'https://joinmastodon.org'
+              %li= link_to t('about.apps'), 'https://joinmastodon.org/apps'
 
 = render template: 'layouts/application'