[FEATURE] CI: JavaScript code-style exception

[thibsy]

Hi folks,

This PR introduces a new rule to our JavaScript code-style in form of an exception/deviation:

Airbnb does not allow to manipulate/reassign parameters completely. However, reassigning parameter properties of e.g. HTMLElements is a common use-case, which has led to many unnecessary variables being initialised to work around this code-style rule. Therefore we allow the manipulation/reassignment of parameter properties.

This partially supersedes Airbnbs ruling to disallow parameter reassignments and will keep our JavaScript code more compact. Note that reassigning a parameter otherwise is still prohibited.

I have updated the according ESLint configuration so these exceptions will no longer be recognised as an error.

Kind regards, @thibsy