Support void (self-closing) HTML elements in mj-raw

[tstriker]

I bumped into this while switching from node version to the python one (which is a port of this lib, i believe).

There is a number of 'void' elements that do not require closing in HTML:
https://developer.mozilla.org/en-US/docs/Glossary/Void_element

however, the lib right now seems to be tripping on them with "unexpected end of stream"

the node version does not seem to have a similar limitation, so seems like could be useful to address these void elements.

thank you for the lib!

[jdrouet]

Hey,
Could you provide an example?
I'm already hunting them but some might not be caught by the CI

[tstriker]

Updated the bug title as i realized that it is specific to contents of mj-raw.
Here's a quick snippet of MJML that triggers the unexpected end of stream:

<mjml>
  <mj-body>
    <mj-raw>
      <img src="bananas">
    </mj-raw>
  </mj-body>
</mjml>