User story: DEV-70: Add eslint dependencies

Description

Adds required dependencies to run ESLint on custom JS.

This branch was tested with palantirnet/the-build#238
and passed tests on CircleCI: https://app.circleci.com/pipelines/github/palantirnet/the-build/589/workflows/fced6b6f-4a86-4e1a-8728-fd3610a1d741/jobs/600

Testing instructions

• Add these dependencies to an existing project's root package.json.
• Update the-build: composer require palantirnet/the-build:dev-DEV-70-update-install-node-dependencies-task-in-the-build
• Make changes from https://github.com/palantirnet/the-build/pull/238/files to the project's build.xml
• ddev phing eslint

Open questions

• Do we want to include all of these dependencies in the skeleton? They were the ones required while testing on a client site.

Remaining tasks

Delete this section if there are no remaining tasks.

• Update the README