Also, refactor ESLint and stylelint config files; now everything will work from our root dir.

We can check for browser compatibility on lint time now.

Ignore ESLint error in ie-emulation-modes-warning.js.

Although the error is valid, enough time has been spent on old IE's problems, so just ignore it.

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Fixes #19908

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Refs #19908

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Refs #19908.

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Refs #19908

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Refs http://eslint.org/docs/user-guide/migrating-to-2.0.0#new-rules-in-eslintrecommended

Refs http://eslint.org/docs/user-guide/migrating-to-2.0.0

Refs #19908

Refs #19908

Enable new rules:
* no-empty-pattern
* no-magic-numbers (exempting 0 and ±1)

Refs #19908

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That way, ESLint won't look in parent dirs for configuration files.

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Closes #17100