Add Relative Position encoding

[jacobbieker]

Pull Request

Description

This is the relative position encoding from #4 as it was getting a bit complicated, and the absolute position encoding is a lot simpler to have implemented.

Fixes #

How Has This Been Tested?

Unit tests

• No
• Yes

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings

[jacobbieker]

After talking over it with @JackKelly closing this for now. Absolute position encoding does give the relative positions in time and space for different inputs, and is simpler. The only benefit this encoding seems to have is that the inputs would stretch from -1 to 1, versus in the absolute encoding, they tend to be a much smaller range.