Use Class and Property Decorators (#3730)

.babelrc

app/javascript/mastodon/components/account.js

app/javascript/mastodon/components/attachment_list.js

app/javascript/mastodon/components/autosuggest_textarea.js

app/javascript/mastodon/components/avatar.js

app/javascript/mastodon/components/avatar_overlay.js

app/javascript/mastodon/components/button.js

app/javascript/mastodon/components/column.js

app/javascript/mastodon/components/column_back_button.js

...javascript/mastodon/components/column_back_button_slim.js

app/javascript/mastodon/components/column_collapsable.js

app/javascript/mastodon/components/column_header.js

app/javascript/mastodon/components/display_name.js

app/javascript/mastodon/components/dropdown_menu.js

app/javascript/mastodon/components/extended_video_player.js

app/javascript/mastodon/components/icon_button.js

app/javascript/mastodon/components/load_more.js

app/javascript/mastodon/components/media_gallery.js

app/javascript/mastodon/components/permalink.js

app/javascript/mastodon/components/relative_timestamp.js