Add full range of same{Unit} functions.

[justin-schroeder]

We currently have sameDay which is a helpful utility to compare two dates with reduced resolution, which I find helpful in many real-world applications. However, it would be nice to include a full range of these utilities:

• sameSecond
• sameMinute
• sameHour
• ~sameDay~ ✅
• sameYear

[hrynevychroman]

@justin-schroeder You can assign this to me, I will add them soon

[hrynevychroman]

@justin-schroeder sameMonth we skip, or you forgot to mention it?

[justin-schroeder]

Thanks @romanhrynevych. we can add sameMonth at some point if youd like