build(vite): replace webpack with Vite, add Typescript (#1594)

BREAKING: mixins are no longer exported from the index (and will likely be converted to hooks)

tsconfig.vitest.json

@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.app.json",
+  "exclude": [],
+  "compilerOptions": {
+    "composite": true,
+    "lib": [],
+    "types": ["node", "jsdom"]
+  }
+}