(fix/deps): build both polyfill & ponyfill entries

- add a polyfill/package.json that points to each format so that
  you can do `import 'window-resizeTo/polyfill'` and get the correct
  version for your usage
  - reconfigures package.json to use `index.esm.js` since names don't
    change with multi-entry

(deps): required upgrading to my fork/PR of TSDX that supports
multi-entry
- and I had to rebase it and fix a bunch of merge conflicts since
  0.12.0 had some issues with things like testing
  - and because it still hasn't been reviewed in 3 months
- also re-configure tsconfig.json to use rootDir: './src' since I
  deprecated the buggy './' and now it gives a warning since I
  updated