Define outline for contributor documentation for ideal package structure

This issue is for creating the outline of what would need to go into the contributor documenation around ideal package structure.

When creating the outline please see the comment from Mark on [Issue 28](https://github.com/MetaMask/contributor-docs/issues/28#issuecomment-1739650251)

As part of this work please get feedback from team to finalize the outline and then create issues for filling in each of the areas of the outline. Please add the tickets to the epic and ensure they are pointed.

Start with Mark's comment on Issue 28, then review the requirements in issue 53 for the contributor documentation outline. Done means a team-reviewed outline for ideal package structure, separate follow-up issues for each area, and those tickets added to the epic with points.

Written by the indexing model from the issue text.