Add new onboarding flow to web UI (#24619)

app/javascript/images/elephant_ui_conversation.svg

app/javascript/mastodon/actions/compose.js

app/javascript/mastodon/components/account.jsx

app/javascript/mastodon/components/check.jsx

app/javascript/mastodon/components/column_back_button.jsx

app/javascript/mastodon/components/status.jsx

app/javascript/mastodon/components/verified_badge.jsx

...ipt/mastodon/features/compose/components/compose_form.jsx

...on/features/follow_recommendations/components/account.jsx

...script/mastodon/features/follow_recommendations/index.jsx

...odon/features/onboarding/components/arrow_small_right.jsx

...don/features/onboarding/components/progress_indicator.jsx

...vascript/mastodon/features/onboarding/components/step.jsx

app/javascript/mastodon/features/onboarding/follows.jsx

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

app/javascript/mastodon/features/onboarding/share.jsx

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

app/javascript/mastodon/features/ui/util/async-components.js

app/javascript/mastodon/locales/defaultMessages.json

app/javascript/mastodon/locales/en.json