Run lint as part of CI

[praneetloke]

@RobbieMcKinstry as discussed, this PR with various miscellaneous fixes. The highlight of the PR is to run lint as part of CI/PR builds. Most of the changes come from the first commit in this PR, which is related to re-enabling code formatting with Prettier.

I also decided to pull out the TaskConfig interface into a type definition file after all, given how much trouble it led to in my previous PR with the incorrect import. It should help avoid similar problems for others in the future.

---

• [x] If you changed the values of the properties name, publisher, and galleryFlags in the vss-extension.json file, you have reverted them.
• [x] If you changed the values of the properties id, name, author, you have reverted them.
• [x] I have reverted any changes to the version number components in both vss-extension.json and task.json, OR I didn't change them.

[AaronFriel]

/azprun

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[AaronFriel]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).