Eslint errors and warnings

 ✖ 1208 problems (1187 errors, 21 warnings)
   831 errors and 0 warnings potentially fixable with the `--fix` option.
 error Command failed with exit code 1.

Eslint job is now part of the Merge Request CI/CD, so it's vital to fix all errors and warnings. For now, the job is allowed to fail, but I will disable it when this issue is done. About half of the errors may be fixed automatically by eslint.