CodeIgniter 4.0 Query Builder and CAST support

Hey man, nice try and thank you for taking care!

I do not want to be a party-braker here, but:
1) you did PR towards wrong repo; right one is https://github.com/codeigniter4/CodeIgniter4
2) you did not cover your change with Unit Tests, so your PR will not be accepted until you extend existing tests for like() method with additional test-cases that cover your changes
3) you have to take care about documentation as well
4) your code smells - but you will know it from maintainers later; particularly - you allow any string as $cast attribute, however, mySQL supports only handful of keywords in their CAST() function - and you mentioned them (INTEGER, DATE, DOUBLE, DOUBLE PRECISION, BOOLEAN, TEXT), but did not add checking and error reporting
5) you should validate your Github account and sign your commit. Read more how to do it here: https://help.github.com/en/github/authen...ng-commits

Good luck with 2nd attempt