Add no-only-tests JS linter rule to detect test.only and suite.only

[pablonete]

This warns on leftovers like suite.only or test.only that would prevent all JS tests from running in CI.

Adding a dependency on this plugin: https://www.npmjs.com/package/eslint-plugin-no-only-tests
It meets the "LAWSUIT" external library criteria:

• Licensing: MIT licensed
• Actively-developed: Latest commit 1 month ago, on June 17th
• Widely-used: 107,289 weekly downloads
• Supply chain safety: only dependency is "eslint"
• Unique functionality: Yes
• Install time impact + bundle size impact: Dev-time linter, no production impact.
• TypeScript support: this doesn't apply to an eslint plugin.

By default, the library doesn't check suite, so I had to change the default value of block by adding it to the default values:

"block": ["describe", "it", "context", "test", "tape", "fixture", "serial", "suite"]

Tested with npm link successfully:

Note: I wasn't able to get npm link to work in Codespaces, I had to use my laptop. I got:
npm was not found in PATH outside of this project
I suspect it's due to npm not being installed in the dotcom Codespace, and even using the bin/npm in the $PATH didn't help.

[koddsson]

This is great! Thank you ❤️