feat(apollo-codegen-typescript): Support scalar JSDoc annotations

[nalchevanidze]

fixes #2544

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.

[apollo-cla]

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[nalchevanidze]

There are some cases and tests that need to be covered, and that will be addressed. But the question is if you like the idea too? We can also implement a more general approach with a plugin interface where I could put this code in the plugin and combine it with the base implementation?