Add floating post-status button on mobile

src/App.js

src/App.scss

src/App.vue

src/boot/routes.js

src/components/media_modal/media_modal.vue

...ents/mobile_post_status_modal/mobile_post_status_modal.js

...nts/mobile_post_status_modal/mobile_post_status_modal.vue

src/components/side_drawer/side_drawer.vue