Switch to ESM

[erjonify]

closes #185

[jimmywarting]

https://github.com/jimmywarting/StreamSaver.js/blob/5b372f7ba5f1e82ef80e2466023930ee2c616a28/StreamSaver.js#L5-L12

• Needs to be removed (and the end of it as well)

• The script tag must be changed to have the type="module"

We can remove all of this:

<script src="https://cdn.jsdelivr.net/npm/web-streams-polyfill@2.0.2/dist/ponyfill.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/streamsaver@2.0.3/StreamSaver.min.js"></script>
<script>
  import streamSaver from 'streamsaver'
  const streamSaver = require('streamsaver')
  const streamSaver = window.streamSaver
</script>

and replace it with:

<script type="importmap">
  {
    "imports": {
      "streamsaver/StreamSaver.js": "https://cdn.jsdelivr.net/npm/streamsaver@3/StreamSaver.min.js"
    }
  }
</script>
<script type="module">
  // either one works fine, the later one requires importmaps or a web bundler. 
  import streamSaver from 'https://cdn.jsdelivr.net/npm/streamsaver@3/StreamSaver.min.js'
  import streamSaver from 'streamsaver/StreamSaver.min.js'

  const uInt8 = new TextEncoder().encode('StreamSaver is awesome')
  ...
</script>

• Every green browser now days have good support for web streams, so i think we can remove the hole shebang where we mention any use of custom stream polyfill

  // StreamSaver can detect and use the Ponyfill that is loaded from the cdn.
  streamSaver.WritableStream = streamSaver.WritableStream
  streamSaver.TransformStream = streamSaver.TransformStream

• also the code examples in https://github.com/jimmywarting/StreamSaver.js/tree/master/examples needs to be changed to also have type="module" in their script tags

[jimmywarting]

Just realized that you created PR #333 (3 threes, 1/3 of 999, threes as in the same length as the amount of number there are in 333) it's also 3:33pm here. and 3 days since you created your first/last commit in this PR! coincident? I think not! 3 is a magic number ✨

[erjonify]

• type="module"

@jimmywarting , i did some small changes, feel free to complete the rest :)