string, bytes assertions: assertContains, assertLt.. etc

[dk1a]

I made a new string slice lib. I like PRBTest, so I made an assertions extension for it (by using PRBMath as an example).
The assertions are for both native string/bytes, and my user-defined StrSlice/Slice types.
https://github.com/dk1a/solidity-stringutils

[PaulRBerg]

Cool stuff! Thanks for sharing.