Make module server configurable

[calebeby]

Closes #140

The code is all ready for review. I didn't update the README yet.

This makes it possible to configure the module server in each test. You could inject additional rollup plugins, etc. An example of this is to add a plugin to load Vue SFC's:

import vuePlugin from 'rollup-plugin-vue'
test(
  'vue component can be imported via rollup-plugin-vue',
  withBrowser(
    {
      moduleServer: {
        plugins: [vuePlugin()],
      },
    },
    async ({ utils, screen }) => {
      await utils.injectHTML('<div id="app"></div>')
      await utils.runJS(`
	    import { createApp } from 'vue'
	    import VueComponent from './vue-component.vue'
	    const app = createApp(VueComponent)
	    app.mount('#app')
	  `)
      const heading = await screen.getByRole('heading')
      await expect(heading).toHaveTextContent('Hiya')
      await expect(heading).toHaveStyle({ color: 'green' })
    },
  ),
)

There is also a configureDefaults function exported by pleasantest, so you don't have to set the options for each test individually:

import { withBrowser, configureDefaults } from 'pleasantest'

configureDefaults({
  moduleServer: {
    plugins: [vuePlugin()],
  },
})

There is also an internal change: File ids (used by the rollup plugins) are now absolute paths once they are resolved. This was changed to match Rollup's default behavior, and it fixed a compatibility issue with rollup-plugin-vue. So the ids start out as url's, which are relative to the project root, then they get converted to absolute paths, and run through all the plugins, and at the very end before the module is served they get converted back into paths that are relative to the project root.

[Paul-Hebert]

This is a killer feature @calebeby !

I'm still wrapping my head around this codebase, but these changes seem reasonable 👍 One nitpick about an error message inline.

[gerardo-rodriguez]

Super cool feature, great work, @calebeby!

I'm in the same boat as @Paul-Hebert where I don't understand every line of code fully but overall, the code looks good! Pending the suggestion from Paul, I approve!

[calebeby]

Thanks for the reviews @Paul-Hebert and @gerardo-rodriguez! Do you mind taking a look at the README changes that I just pushed as well?

[Paul-Hebert]

@calebeby the README info looks good! I left a couple questions inline.