Only activate extension on apollo.config.js/ts

[trevor-scheer]

Activating the extension on package.json is potentially obnoxious for non-apollo projects, and breaks for projects that don't use a package file. Activating on apollo.config.js works across all project types and keeps the extension quiet for non-apollo projects.

TODO:

• Update CHANGELOG.md* with your change (include reference to issue & this PR)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

*Make sure changelog entries note which project(s) has been affected. See older entries for examples on what this looks like.

[JakeDawkins]

@trevor-scheer I can't get this version of the extension to activate anywhere, in any project after building/installing it.