lint + fixes for registration

src/components/color_input/color_input.vue

src/components/notification/notification.vue

src/components/opacity_input/opacity_input.vue

src/components/poll/poll.vue

src/components/registration/registration.js

src/components/registration/registration.vue

src/components/selectable_list/selectable_list.vue

src/components/settings_modal/helpers/boolean_setting.vue

src/components/settings_modal/helpers/choice_setting.vue

src/components/settings_modal/settings_modal.vue

src/components/settings_modal/tabs/profile_tab.vue

src/components/thread_tree/thread_tree.vue

src/components/user_avatar/user_avatar.vue

src/components/user_reporting_modal/user_reporting_modal.vue