Refactoring: moving to Composition API

[Igor]

I created this issue so we can keep track of which files are being changed and avoid conflicts.

• ./src/App.vue
• ./src/components/AddonManager.vue
• ./src/components/Chat.vue
• ./src/components/Error.vue
• ./src/components/Footer.vue
• ./src/components/Header.vue
• ./src/components/Loading.vue
• ./src/components/Settings.vue
• ./src/components/player/LockScreen.vue
• ./src/components/player/Player.vue
• ./src/components/player/Subtitle.vue
• ./src/components/player/controls/AutoSync.vue
• ./src/components/player/controls/FullScreen.vue
• ./src/components/player/controls/Hls.vue
• ./src/components/player/controls/PlayPause.vue
• ./src/components/player/controls/Subtitles.vue
• ./src/components/player/controls/TimeBar.vue
• ./src/components/player/controls/Volume.vue
• ./src/components/ui/Button.vue
• ./src/components/ui/Link.vue
• ./src/components/ui/List.vue
• ./src/components/ui/RangeInput.vue
• ./src/components/ui/Segments.vue
• ./src/components/ui/Select.vue
• ./src/components/ui/TextInput.vue
• ./src/components/ui/Title.vue
• ./src/views/Home.vue
• ./src/views/Room.vue
• ./src/views/Search.vue
• ./src/views/Stream.vue