add sum sumBy and CountIf functionality to ResArr

[DoganCK]

Added simple functionality to ResizeArray.
They will help Graphoscope code to be more readable and performant.

[kMutagene]

Hey @DoganCK, thanks for the additions. Could you add some basic tests accompanying this PR?

[DoganCK]

Sure @kMutagene just added them.

[kMutagene]

Thanks! last request i promise :D

Could you add xml documentation above the functions, also documenting the parameters? See

FSharpAux/src/FSharpAux.Core/Dictionary.fs

Lines 9 to 11 in a235fd3

	/// <summary>Views the collection as an enumerable sequence of pairs.
	/// The sequence will be ordered by the keys of the dictionary.</summary>
	/// <param name="table">The input dictionary.</param>

for example. I know the other functions in this module completely lack this, but let's lead by example 😆

[DoganCK]

Sure @kMutagene, that's a good idea! I've added docs for the three functions.
Planning to add more but I'll create a new PR for those.

By the way this is a really useful library, any plans to move it over to FsLab?

[kMutagene]

Thank you @DoganCK !

Happy that you find the lib useful. I have not thought about moving it to fslab because it lacks a data science specific focus, we can however discuss this further.