Copy the strawman FAQ as an overview page

[lrytz]

This creates a 1:1 copy of https://github.com/scala/collection-strawman/wiki/FAQ with the goal to have a stable URL for the document. Follow-up changes are required: some content is outdated, issues with the layout (the tables are too wide).

[julienrf]

Since the table does not render well and it only has few entries, we could just replace table rows with paragraphs:

### Operation `to[C[_]]`

Operation `to[C[_]]` has been removed.

Scala 2.12 code:

```scala
xs.to[List]
```

Scala 2.13 code:

```scala
xs.to(List)
```

Automatic migration rules: `Collection213Upgrade` and `Collections213CrossCompat`

[lrytz]

i left the tables for now. not sure what's the best way to fix it... is there something like a scroll-div we can use? for code blocks that is done automatically.

[lrytz]

I know that this doc isn't in the best possible shpae yet, but I'd suggest to not go too deep right now and refine it once it's merged. It's useful to have a stable link to what we have now.

[julienrf]

The content looks good, but we should make sure the page renders well before we publish it.

[lrytz]

Agreed. I'll give it a try.

[lrytz]

Added some div wrapper to allow scrolling - wdyt?
https://www.youtube.com/watch?v=WqB_aHKzVLA

[julienrf]

It works but the right columns are not easily discovered. We can improve that later, though.

[lrytz]

I changed the FAQ to point to the scala-lang page (https://github.com/scala/collection-strawman/wiki/FAQ)

[SethTisue]

I updated the link at https://github.com/scala/scala/releases/tag/v2.13.0-RC1