Use proper markdown rendering for previews

app/assets/javascripts/issue_show/components/app.vue

.../javascripts/issue_show/components/fields/description.vue

app/assets/javascripts/issue_show/components/form.vue

app/assets/javascripts/notes.js

app/assets/javascripts/notes/components/comment_form.vue

app/assets/javascripts/notes/components/note_body.vue

app/assets/javascripts/notes/components/note_form.vue

app/assets/javascripts/notes/components/notes_app.vue

app/assets/javascripts/notes/index.js

app/assets/javascripts/preview_markdown.js

...sets/javascripts/vue_shared/components/markdown/field.vue

app/controllers/concerns/preview_markdown.rb

app/helpers/issuables_helper.rb

app/helpers/markup_helper.rb

app/helpers/notes_helper.rb

app/models/concerns/cache_markdown_field.rb

app/models/repository.rb

app/serializers/note_entity.rb

app/services/preview_markdown_service.rb

app/views/projects/issues/_form.html.haml