I've added some additional context to the doc in efforts to explain the
memory management system to users. After this, I'm going to write a bit
more about the actual implementation of the system as it stands
currently. One of the goals of this effort is to make it easier to
upgrade given an exhaustive account of its present workings.

The start of some additional introductory documentation on the memory
management system's key operations.

Describes the basics of copying references. More to come.

The memory doc now contains an approachable explanation of basic linear
type system concepts. I plan on extending this exploration with some
detailed explorations of the implementation.

- Remove a comma.
- Mention registered types.

- Fix a typo
- Mention `ref`
- Describe that `typedef` defined types are automatically given delete
  implementations and managed by default.