Fix the typescript type declaration

[lulu-berlin]

In typescript (with webpack), a default import doesn't work:

import ResizeObserver from 'resize-observer-polyfill';

but a star import or an import = require import do work:

import * as ResizeObserver from 'resize-observer-polyfill';

or:

import ResizeObserver = require('resize-observer-polyfill');

Apparently there is a closed issue about this. This fixes #24.

[walkerburgin]

We lost an hour to this today

[lulu-berlin]

We lost an hour to this today

Sorry, @walkerburgin, seems like this repository is not being maintained... My PR has been left hanging for a long time.

We have created a fork in our organization with this fix applied: https://github.com/bettermarks/resize-observer-polyfill