Delay __karma__.start() until es6 test modules have been loaded

[dwt]

If unit tests are loaded from modules (which is supported via the files configuration option) then __karma__.start() should really be delayed until after all the modules have been loaded, to give unit tests the ability to load before the start event.

I'm not sure about all test frameworks, but at least for jasmine it is necessary, as you cannot add tests to it, after it has started executing all it's configured tests.

So with a configuration like this:

    files: [
      { pattern: 'static/vendor/**/*.js', watched: false },
      { pattern: 'static/*.js', type: 'module', included: false },
      { pattern: 'static/tests/*.js', type: 'module' },
    ],

I would really like the context.html to read

  <script type="module">
    window.__karma__.loaded();
  </script>
  <script nomodule type="text/javascript">
    alert("your browser doesn't support modules, use a different one")
  </script>

instead of

  <script type="text/javascript">
    window.__karma__.loaded();
  </script>

which it is currently executing.

Not quite sure what the best way to patch this in would be, but it seems to work great for me in local tests.

So: are there any downsides to this approach? How would you be willing to take this as a pull request?

[dwt]

Hm, I just realized that this is the wrong project to report this. Moving it now.