Lints the cypress system tests

[laoneo]

Adds he cypress specs to the linter for testing. The override is needed in the config file, so all the functions and the global "cy" variable are not reported as undefined.

[laoneo]

@dgrammatiko can yo have a look here if did not miss anything?

[dgrammatiko]

LGTM

FWIW if you want to be way more strict what could be done is:

• in the package.json split the lint script so that it could check the build and tests folders independently, with different configurations.
• copy the existing config and add the https://www.npmjs.com/package/eslint-plugin-chai-friendly and https://www.npmjs.com/package/eslint-plugin-cypress

[laoneo]

For now I would leave it as it is, without adding another dev dependency. We can do that later when we have the need for it.