[Embeds] Create vite project and add to build pipeline (#3448)

* add bskyembed vite app

* create build script (temp until embedr is ready)

bskyembed/vite.config.ts

@@ -0,0 +1,18 @@
+import {resolve} from 'node:path'
+
+// @ts-expect-error - not important
+import preactRefresh from '@prefresh/vite'
+import type {UserConfig} from 'vite'
+import paths from 'vite-tsconfig-paths'
+
+const config: UserConfig = {
+  jsx: {
+    factory: 'h',
+    fragment: 'Fragment',
+  },
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-call
+  plugins: [preactRefresh(), paths()],
+  assetsDir: 'static/embed/assets',
+}
+
+export default config