Add contains() method to check if an index is within array bounds

[theoxfaber]

Adds a contains() method to ArrayBase to check whether a given index falls within array dimensions without accessing the element.

Closes #1247

let a = arr2(&[[1., 2.], [3., 4.]]);
assert!(a.contains((0, 1)));
assert!(!a.contains((2, 0)));

[akern40]

Could you please add a test or two on the new method? And rebase off of master as well, to fix potential CI issues