Wrong signature in assertions documentation

[JpOnline]

After the .isExtensibleObject, all the methods miss the optional message parameter in the documentation.

[keithamus]

Thanks for the issue @JpOnline! Want to make a PR to fix this?

[Hpauric]

Hey, I can make those fixes, if that suits? Looks like .ifError(object) is missing the optional message parameter also.

[keithamus]

Sounds great 👌. Look forward to seeing the PR @Hpauric

[meeber]

Fixed by #1023