Add markdown preview to Submit Review Textarea (#24672)

Before:

![image](https://github.com/go-gitea/gitea/assets/18380374/2909352c-b2ab-4d77-b410-9f08c2f5a154)

After:

![image](https://github.com/go-gitea/gitea/assets/18380374/9448fa75-e29b-4f95-a30f-03c73c083a83)

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

templates/repo/diff/new_review.tmpl

@@ -9,13 +9,15 @@
 			<form class="ui form" action="{{.Link}}/reviews/submit" method="post">
 				{{.CsrfTokenHtml}}
 				<input type="hidden" name="commit_id" value="{{.AfterCommitID}}">
-				<div class="header gt-df gt-ac gt-pb-3">
+				<div class="field gt-df gt-ac">
 					<div class="gt-f1">{{$.locale.Tr "repo.diff.review.header"}}</div>
-					<a class="muted close gt-px-3">{{svg "octicon-x" 16}}</a>
+					<a class="muted close">{{svg "octicon-x" 16}}</a>
 				</div>
-				<div class="ui field">
+				<div class="field">
 					{{template "shared/combomarkdowneditor" (dict
 						"locale" $.locale
+						"MarkdownPreviewUrl" (print .Repository.Link "/markup")
+						"MarkdownPreviewContext" .RepoLink
 						"TextareaName" "content"
 						"TextareaPlaceholder" ($.locale.Tr "repo.diff.review.placeholder")
 						"DropzoneParentContainer" "form"

web_src/css/code/linebutton.css

@@ -4,6 +4,7 @@
 
 .code-line-menu {
   width: auto !important;
+  border: none !important; /* the border is provided by tippy, not using the `.ui.menu` border */
 }
 
 .code-line-button {

web_src/css/modules/tippy.css

@@ -29,10 +29,6 @@
   color: var(--color-tooltip-text);
 }
 
-.tippy-box[data-theme="menu"] .ui.menu {
-  border: none;
-}
-
 .tippy-content {
   position: relative;
   padding: 1rem;