[Tutorial] Write tutorial pages for compilation API

[jkwak-work]

We need tutorial pages for people who want to learn about the compilation API. The tutorial should also reflect some of high level principles of Slang language design that Tess presented at a recent brown-bag.

Specifically we need to fill in the TODO sections in a commit.

There are multiple "TODO" lines in the commit. This issue is for the following sections:

docs/compilation-api.md