eslint: ignore yarn directory and backup files

[stefanv]

While completing the exercises, yarn created a .yarn directory that created problems with the linter.

Emacs stores backup files as #<something>#, and these files also shouldn't be checked.

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[stefanv]

Any thoughts on this PR?

[SleeplessByte]

I don't wholly understand why https://github.com/exercism/eslint-config-typescript/blob/main/eslint.config.mjs#L10 is not capturing this (and why I don't have the issue locally).

I am not opposed to this PR if it fixes the issue for you (and everyone else), but I would like to understand why it's not picking up that ignore!

[SleeplessByte]

...and the answer is of course because we don't import that file :')

Eh. Yah. Okay.

'**/#*'
'.appends/**/*',
'.github/**/*',
'.vscode/**/*',
'.yarn/**/*',
'.pnp.*',
'node_modules/**/*',
'babel.config.cjs',
'jest.config.cjs',

This is probably the full list we need to ignore for generated / tooling?

If you agree, can you extend the list further adding the missing entries, and add an extra PR to the repo I linked above to add **/#* as well? If you link your GitHub to your Exercism account, you'll receive reputation for both.

Thanks for this @stefanv !

[SleeplessByte]

@stefanv would you still like to contribute this PR?