fix: vs extension lint error

[patricksullivansf]

Summary

Fixes lint error

% pnpm lint
...
packages/b2c-vs-extension lint$ eslint
...
│ A configuration object specifies rule "@typescript-eslint/no-unused-vars", but could not find plugin "@typescript-eslint".

• update lint configuration
• always run lint as part of test
• reformat files so linting passes
• added vs extension linting to CI (assuming testing can't be done on CI since it launches vscode)

Testing

Start with a fresh clone, run pnpm install, pnpm lint
Or pnpm install, pnpm test

Dependencies

• No net-new third-party dependencies were added
• If net-new third-party dependencies were added, rationale/discussion is included and 3pl-approved is set by a maintainer

---

• Tests pass (pnpm test)
• Code is formatted (pnpm run format)

[wei-liu-sf]

can you add pnpm lint as one of PR requirements in PR template?

[patricksullivansf]

can you add pnpm lint as one of PR requirements in PR template?

Added "posttest": "pnpm run lint" to vs ext project.json, which should be consistent with other projects. (pnpm test is already in the template).