upgrade eslint to latest version

[chenxsan]

I was trying to document import.meta.url introduced in webpack v5.0.0-beta.21 only to find that the current eslint (v4.19.1) we have threw error because the import.meta feature was added in eslint v7.2.0.

This PR should upgrade eslint to the latest version so we can document more advanced JavaScript features that webpack supports.

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[chenxsan]

CI failed when updating babel-eslint to v9, related issue babel/babel-eslint#799

[chenxsan]

After replacing babel-eslint with @babel/eslint-parser, CI failed because we have some typescript typings in JavaScript code block https://github.com/webpack/webpack.js.org/blob/master/src/content/api/module-methods.md#require which is not valid JavaScript:

require.resolve(dependency: String);

[chenxsan]

Now we're able to use import.meta.url in JavaScript code block:

[alexander-akait]

Good job!

[alexander-akait]

Good job!

[EugeneHlushko]

LGTM, nice to see the eslint ignore comments gone :)

[EugeneHlushko]

Thanks!