Add `depcheck`-related checks

[mcmire]

We want to make sure that for a given project:

• The project contains depcheck as a dev dependency, and the version matches the same dev dependency as in the module template.
• The project contains a lint:dependencies package script, and this package script runs depcheck (i.e. the value of this script matches /\bdepcheck\b/).
• If the lint script exists, then it runs yarn lint:dependencies (i.e. the value of this script matches /\byarn lint:dependencies\b/)
• The project contains a .depcheckrc.json file.
• Go through the list of ignores in .depcheckrc.json in the module template; for each one listed there:
  • If the ignore is not @types/*, and it is in the project's dependencies, then it should be in the project's .depcheckrc.json
  • If the ignore is @types/*, then for each of the project's dependencies that are under the @types scope, it should also be listed in the project's .depcheck.json

[desi]

@mcmire will update module template to use yml file first then change the above requirements to use that instead.