Add eslint

[dominik-zeglen]

I want to merge this change because it adds eslint 🎉
Pls notice that I disabled some rules that are meant to be fixed later - it's not possible to fix all 1000 problems with one PR.

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. The changes are tested.
4. The code is documented (docstrings, project documentation).
5. Changes are mentioned in the changelog.

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging e4fc4d5 into 4348639 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

fixed alerts:

• 1 for Unused or undefined state property

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging abfae48 into 4348639 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

fixed alerts:

• 1 for Unused or undefined state property

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging ee6e47a into 4348639 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

fixed alerts:

• 1 for Unused or undefined state property

[krzysztofwolski]

Fix CI and can be merged

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging 9f8b272 into a795cda - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

fixed alerts:

• 1 for Unused or undefined state property