fix: Correct file ignore check for node_modules

[andyrooger]

Fixes issue where all node_modules and non-ts(x) files are linted even if they're explictly ignored by eslint config.
Also correcting file path check on Windows.

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#528 fixed most of our problems running on Windows. Unfortunately, it didn't seem to quite fix the code that ignores linting for node_modules.

After some investigation it turns out on Windows, the checkFileToBeIgnored method sometimes receives files as standard Windows paths (\) but sometimes with forward slashes.

This should fix the issue properly. Apologies to @artola for contributing the dodgy fix to your PR 🙂

[andyrooger]

Edit: Assuming the intention is to hardcode ignoring node_modules and non-ts for performance

OK, we've been running with this on a few machines for a while. It turns out this does fix the check, but the behaviour doesn't seem right. It looked like it worked because it takes maybe an hour before the lint errors start appearing in the IDE (it has a lot to churn through)

If checkFileToBeIgnored determines a file to be from node_modules or not a TS file, then it skips the check and always lints it, even it's it's explicitly listed as ignored in the eslint config.

@Quramy Do you remember what the initial intention of this code was?
@artola Or do you have any insights into it?

I'm running this in VS Enterprise, does that make a difference to which files pass through here? e.g. Does VS code not try to lint node_modules so we didn't need to check?

[andyrooger]

Closing in favour of #543