Render embedded code preview by permlink in markdown (#30234) (#30249)

Backport #30234 by wxiaoguang

The permlink in markdown will be rendered as a code preview block, like GitHub

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

services/contexttest/context_tests.go

@@ -63,6 +63,7 @@ func MockContext(t *testing.T, reqPath string, opts ...MockContextOption) (*cont
 	base.Locale = &translation.MockLocale{}
 
 	ctx := context.NewWebContext(base, opt.Render, nil)
+	ctx.AppendContextValue(context.WebContextKey, ctx)
 	ctx.PageData = map[string]any{}
 	ctx.Data["PageStartTime"] = time.Now()
 	chiCtx := chi.NewRouteContext()