Fix Vite dependency extract

[palicko]

Hey,
first of all, great job implementing Vite to the Sage, I love it!

Dependency extraction regex is working fine when imports are defined in single line, but not working when imports are defined using new lines, e.g.

import {
  InnerBlocks,
  InspectorControls,
  RichText,
  useBlockProps,
  useInnerBlocksProps,
} from '@wordpress/block-editor';

This PR should fix regex and add check if extracted import is not empty (last comma in import block was causing trouble).

Also I've added small fix for Typescript compatibility.

[retlehs]

Thank you!