Add edit option for README.md (#28071)

Fix #28059


![grafik](https://github.com/go-gitea/gitea/assets/15185051/07adc216-954e-486b-bfda-df3bc15f2089)

routers/web/repo/view.go

@@ -331,6 +331,10 @@ func renderReadmeFile(ctx *context.Context, subfolder string, readmeFile *git.Tr
 
 		ctx.Data["FileContent"] = buf.String()
 	}
+
+	if !fInfo.isLFSFile && ctx.Repo.CanEnableEditor(ctx, ctx.Doer) {
+		ctx.Data["CanEditReadmeFile"] = true
+	}
 }
 
 func renderFile(ctx *context.Context, entry *git.TreeEntry, treeLink, rawLink string) {

templates/repo/view_file.tmpl

@@ -61,6 +61,9 @@
 				<button class="ui mini basic button unescape-button gt-mr-2 gt-hidden">{{ctx.Locale.Tr "repo.unescape_control_characters"}}</button>
 				<button class="ui mini basic button escape-button gt-mr-2">{{ctx.Locale.Tr "repo.escape_control_characters"}}</button>
 			{{end}}
+			{{if and .ReadmeInList .CanEditReadmeFile}}
+				<a class="btn-octicon" data-tooltip-content="{{ctx.Locale.Tr "repo.editor.edit_this_file"}}" href="{{.RepoLink}}/_edit/{{PathEscapeSegments .BranchName}}/{{PathEscapeSegments .TreePath}}/{{PathEscapeSegments .FileName}}">{{svg "octicon-pencil"}}</a>
+			{{end}}
 		</div>
 	</h4>
 	<div class="ui attached table unstackable segment">