core: add welcome page

packages/ui-default/handler.ts

@@ -68,6 +68,7 @@ class WikiHelpHandler extends Handler {
     const languages = {};
     for (const key in LANGS) {
       if (LANGS[key].domain && !LANGS[key].domain.includes(domainId)) continue;
+      if (LANGS[key].hidden) continue;
       languages[`${LANGS[key].display}(${key})`] = LANGS[key].compile || LANGS[key].execute;
     }
     this.response.body = { languages };