Rewrite `<Skeleton/>` as FC and TS (#25055)

app/javascript/mastodon/components/admin/Counter.jsx

app/javascript/mastodon/components/admin/Dimension.jsx

app/javascript/mastodon/components/display_name.tsx

app/javascript/mastodon/components/empty_account.tsx

app/javascript/mastodon/components/hashtag.jsx

app/javascript/mastodon/components/server_banner.jsx

app/javascript/mastodon/components/skeleton.jsx

app/javascript/mastodon/components/skeleton.tsx

app/javascript/mastodon/features/about/index.jsx

...javascript/mastodon/features/explore/components/story.jsx

app/javascript/mastodon/features/privacy_policy/index.jsx