implement namespaced components

[Rich-Harris]

This allows components to be member expressions — so instead of this...

<script>
  import {
    Scene,
    PerspectiveCamera,
    OrbitControls,
    AmbientLight,
    DirectionalLight,
    Plane,
    Box
  } from '@sveltejs/gl';
</script>

<Scene>
  <OrbitControls let:location let:target>
    <PerspectiveCamera {location} {target}/>
  </OrbitControls>

  <DirectionalLight direction={[-1,-1,-1]} intensity={0.8}/>

  <Plane
    color={0xffffff}
    location={[0,-0.01,0]}
    rotation={[-90,0,0]}
    scale={10}
  />

  <Box location={[0,0.5,0]}/>
</Scene>

...you can do this:

<script>
  import * as GL from '@sveltejs/gl';
</script>

<GL.Scene>
  <GL.OrbitControls let:location let:target>
    <GL.PerspectiveCamera {location} {target}/>
  </GL.OrbitControls>

  <GL.DirectionalLight direction={[-1,-1,-1]} intensity={0.8}/>

  <GL.Plane
    color={0xffffff}
    location={[0,-0.01,0]}
    rotation={[-90,0,0]}
    scale={10}
  />

  <GL.Box location={[0,0.5,0]}/>
</GL.Scene>

[Conduitry]

Aside from the test failures, this also does not update the vars stuff or the missing-declaration warnings appropriately.

[Rich-Harris]

Well caught, thanks. Fixed

[Conduitry]

Did it not seem safe to just roll this logic into warn_if_undefined itself instead?

[Conduitry]

Eh, I guess you need to add_reference here with it anyway. It might be nice though if warn_if_undefined didn't require an extra name arg as well as the info arg.

[Conduitry]

It's silly to let this hold up the PR actually, gonna go ahead an approve