[Glitch] Add server thumbnail alt text to frontend

Port 3473b8a652 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/about/index.jsx

@@ -82,7 +82,14 @@ class About extends PureComponent {
       <Column bindToDocument={!multiColumn} label={intl.formatMessage(messages.title)}>
         <div className='scrollable about'>
           <div className='about__header'>
-            <ServerHeroImage blurhash={server.getIn(['thumbnail', 'blurhash'])} src={server.getIn(['thumbnail', 'url'])} srcSet={server.getIn(['thumbnail', 'versions'])?.map((value, key) => `${value} ${key.replace('@', '')}`).join(', ')} className='about__header__hero' />
+            <ServerHeroImage
+              withAltBadge
+              alt={server.getIn(['thumbnail', 'description']) ?? ''}
+              blurhash={server.getIn(['thumbnail', 'blurhash'])}
+              src={server.getIn(['thumbnail', 'url'])}
+              srcSet={server.getIn(['thumbnail', 'versions'])?.map((value, key) => `${value} ${key.replace('@', '')}`).join(', ')}
+              className='about__header__hero'
+            />
             <h1>{isLoading ? <Skeleton width='10ch' /> : server.get('domain')}</h1>
             <p><FormattedMessage id='about.powered_by' defaultMessage='Decentralized social media powered by {mastodon}' values={{ mastodon: <a href='https://joinmastodon.org' className='about__mail' target='_blank' rel='noopener'>Mastodon</a> }} /></p>
           </div>