chore: add default docs theme

docs/.vitepress/theme/docs.css

@@ -0,0 +1,8 @@
+:root {
+  --vp-home-hero-name-color: transparent;
+  --vp-home-hero-name-background: -webkit-linear-gradient(
+    120deg,
+    #0a0abc,
+    #24a0ff
+  );
+}

docs/.vitepress/theme/index.ts

@@ -0,0 +1,21 @@
+import type { Theme } from 'vitepress'
+import DefaultTheme from 'vitepress/theme'
+// https://vitepress.dev/guide/custom-theme
+import { h } from 'vue'
+import './docs.css'
+
+// import TwoSlashFloatingVue from 'vitepress-plugin-twoslash/client'
+
+export default {
+  extends: DefaultTheme,
+
+  Layout: () => {
+    return h(DefaultTheme.Layout, null, {
+      // https://vitepress.dev/guide/extending-default-theme#layout-slots
+    })
+  },
+
+  // enhanceApp({ app }: EnhanceAppContext) {
+  //   app.use(TwoSlashFloatingVue)
+  // },
+} satisfies Theme