Support overriding <script type={}>

[EricRabil]

This enables Django sites to render both <script type="module"> and <script nomodule> tags using this library.

Used as such:

{% render_bundle 'main' jsType='module' %}
{% render_bundle 'main' config='legacy' attrs='nomodule' %}

[andersk]

Can we just get rid of the type="text/javascript" (#152, #170)? It’s unnecessary and even discouraged by the specification: “Authors should omit the type attribute instead of redundantly setting it.” It causes the validator to raise warnings, too.

Then a user could set type="module" using the existing attrs mechanism.

[fjsj]

Fixed by #170