Merge branch 'fix-mentions-new-bugs' into 'develop'

src/components/chat_message/chat_message.scss

src/components/chat_title/chat_title.vue

src/components/mention_link/mention_link.js

src/components/mention_link/mention_link.scss

src/components/mention_link/mention_link.vue

src/components/mentions_line/mentions_line.scss

src/components/popover/popover.vue

src/components/rich_content/rich_content.jsx

src/components/settings_modal/tabs/general_tab.vue

src/components/status/status.scss

src/components/status/status.vue

src/components/still-image/still-image.js

src/components/still-image/still-image.vue

src/components/user_card/user_card.vue

src/components/user_list_popover/user_list_popover.vue

src/i18n/en.json

src/modules/config.js

src/modules/instance.js

src/services/html_converter/html_tree_converter.service.js

test/unit/specs/components/rich_content.spec.js