Migrated from JSHint to ESLint

[Nishthajain7]

Fixes #1540

Changes: Updated the preprocessing lint step to use ESLint instead of JSHint.

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• has no typecheck errors (npm run typecheck)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123
• meets the standards outlined in the accessibility guidelines

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[khanniie]

Hi! Thank you so much for the contribution! If this is regarding the codemirror 5 to 6 migration, the subissue we published was actually regarding the js linter used within the Editor/stateUtils.js file. I do think the approach is correct, it would be great if you could move the changes to that file!

[Nishthajain7]

Sorry for the delay. There were a lot of emails, and this one slipped through. I've moved the changes to stateUtils.js

[khanniie]

Hi Nishthajain7! I checked out the branch and it doesn't build properly -- it looks like eslint-linter-browserify isn't installed in the package.json? Would you be able to address this? Thanks!

[khanniie]

maybe we can import this as import {Linter as ESLint} to keep the naming clear?