forbid .bind and instead propose fat arrow method alternative

[tomholub]

I thought I have forbidden .bind with a linter, but it looks like I didn't. I'll make another issue.

Originally posted by @tomholub in #3198 (comment)

[tomholub]

Yes, actually in some other programming languages (C#) when you pass a reference to a method (opgpKey.getEncryptionKey) this reference actually includes this reference for the non-static method (opgpKey). For Javascript, I have to bind opgpKey explicitly so that getEncryptionKey will see it as this.
Of course we can bind it via lambda like getEncryptionKey = (params) => opgpKey.getEncryptionKey(params) if you're more comfortable with this programming-style binding.