This PR adds support for Geometric & Harmonic mean along with tests coverage for these implementations.

Note:

At present, weights must be passed as an empty list ([]) rather than None or no argument. This is due to a Mojo limitation (iirc resolved in the latest nightly builds) where Optional[List[T]] cannot be passed as a read argument because List does not conform to ImplicitlyCopyable.

An alternative design would be to define gmean as:

fn gmean(data: List[Float64], weight: Optional[List[Float64]]=None) -> Float64:

However, this would require explicitly constructing an Optional[List[Float64]] at the call site:

var x = [1.0, 4.0, 7.0]
var w = Optional([3.0, 1.0, 3.0])
var res = gmean(x, w)

For now, we can standardize on using either one of the possibilities and revisit this in future when mojo let's us pass the List[Float64] such that we can do the following,

var x = [1.0, 4.0, 7.0]
var res = gmean(x) # weights default to None for the Optional[List[Float64]]

var x2 = [1.0, 2.0, 3.0]
var weights2 = [1.0, 2.0, 3.0]
var res2 = gmean(x2, weights2) # this is what we want in future.