forgejo/templates/repo/issue/comment_tab.tmpl

<div class="field">
  <div class="ui top attached tabular menu" data-write="write" data-preview="preview">
    <a class="active item" data-tab="write">{{.i18n.Tr "repo.release.write"}}</a>
    <a class="item" data-tab="preview"  data-url="{{AppSubUrl}}/api/v1/markdown" data-context="{{.RepoLink}}">{{.i18n.Tr "repo.release.preview"}}</a>
  </div>
  <div class="ui bottom attached active tab segment" data-tab="write">
    <textarea id="content" name="content" tabindex="4"></textarea>
  </div>
  <div class="ui bottom attached tab segment markdown" data-tab="preview">
    {{.i18n.Tr "repo.release.loading"}}
  </div>
</div>
{{if .IsAttachmentEnabled}}
<div class="attachments"></div>
<div class="ui basic button dropzone" id="dropzone" data-upload-url="{{AppSubUrl}}/issues/attachments" data-accepts="{{.AttachmentAllowedTypes}}" data-max-file="{{.AttachmentMaxFiles}}" data-max-size="{{.AttachmentMaxSize}}" data-default-message="{{.i18n.Tr "dropzone.default_message"}}" data-invalid-input-type="{{.i18n.Tr "dropzone.invalid_input_type"}}" data-file-too-big="{{.i18n.Tr "dropzone.file_too_big"}}" data-remove-file="{{.i18n.Tr "dropzone.remove_file"}}"></div>
{{end}}