Added button to copy file name in PR files (#35509)

The merge request file viewer has a button for copying the file path,
but it is not always convenient. Often, you only want to copy the file
name, which is currently not possible. This change request adds this
capability.

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: a.kiselev <a.kiselev@reglab.ru>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/diff/box.tmpl

@@ -143,6 +143,7 @@
 											<button class="unescape-button item" data-unicode-content-selector="#diff-{{$file.NameHash}}">{{ctx.Locale.Tr "repo.unescape_control_characters"}}</button>
 											<button class="escape-button tw-hidden item" data-unicode-content-selector="#diff-{{$file.NameHash}}">{{ctx.Locale.Tr "repo.escape_control_characters"}}</button>
 										{{end}}
+										<button class="item" data-clipboard-text="{{$file.GetDiffFileBaseName}}">{{ctx.Locale.Tr "copy_filename"}}</button>
 										{{if not $.PageIsWiki}}
 											{{if $file.IsDeleted}}
 												<a class="item" rel="nofollow" href="{{$.BeforeSourcePath}}/{{PathEscapeSegments .Name}}">{{ctx.Locale.Tr "repo.diff.view_file"}}</a>