Add isNumber Predicate

[CMiksche]

Problem to solve

For checking if a return value is a number we have isFloat or isInteger. However I can't check if it is one of either.

I use some APIs where the return value can either be a float or integer - so in my case I just want to check if the return value is a number.

Proposal

For cases like this, I would love a new Predicate isNumber which can be used to check if the return value is some kind of number like float or integer.

Additionally, it would be nice to have some kind of OR or || operator - that would also solve this Issue because I would be able to write `isFloat OR isInteger

Tasks to complete

• Create isNumber Predicate which should be valid if the response is either a float or integer
• Add OR or || operator

[jcamiel]

@CMiksche the predicate isNumber will be available in 4.3.0 (release soon), thanks @guerinoni for the PR