Allow co-location of support components

[NullVoxPopuli]

For example:

docs/
  {whateverPath}
    home/
      index.md
      content-a.hbs
      content-b.hbs
      content-c.gjs
      content-d.gts
      etc

this way, you don't need to place components in totally unrelated places in your docs app. co-location for everything.

In the index.md, it could have snippets like:

# My Heading

```gjs live
import { ContentC } from './content-c';
import { default as ContentB } from './content-b';

<template>
  <ContentC />
  <CnotentB />
</template>
```

```gjs live
import ContentA from './content-a';

<template>
  <ContentA @arg={{2}} />
</template>
```