Add changelog-related checks

[mcmire]

We want to make sure that for a given project:

• The project contains a CHANGELOG.md, and it is valid (i.e., running it through auto-changelog's validate function passes).
  • We would also want to make sure that module-lint is using the same version of auto-changelog as the module template.
• The project contains @metamask/auto-changelog as a dev dependency, and the version matches the same dev dependency as in the module template.
• The project contains the same lint:changelog package script as in the module template
• If the lint script exists, then the lint script runs yarn lint:changelog (i.e. the value of this script matches /\byarn lint:changelog\b/).

[mcmire]

For more context on this item:

The project contains a CHANGELOG.md, and it is valid (i.e., running it through auto-changelog's validate function passes).

The auto-changelog package has a validateChangelog function that can be imported. The idea here would be to call this function in the rule; if this function throws (meaning the changelog is invalid) then the rule should fail, but if it is not, then it should pass.

[kanthesha]

@mcmire your thoughts on running yarn lint:changelog with exec (from child_process)?