[#1212] Switch TSlint to ESlint

[eonarheim]

===:clipboard: PR Checklist :clipboard:===

• 📌 issue exists in github for these changes
• 🔬 existing tests still pass
• 🙈 code conforms to the style guide
• 📐 new tests written and passing / old tests updated with new scenario(s)
• 📄 changelog entry added (or not needed)

==================

Closes #1212

Changes:

• Update source where needed with new eslint rules
• Add eslint config + dependencies
• Update build process to use eslint

[kamranayub]

I like it, nice job. 👍