feat(types): Enable types when importing from /src

Previously, when using the 'Advanced Installation' method outlined
in docs, types would be unavailable. By providing an index.d.ts
file in /src, types become available whether importing from the
compiled package or importing from the package source.

Author: gristow

packages/svelte-materialify/src/index.d.ts

@@ -0,0 +1 @@
+export * from '../@types/index';