Clarify semantics of include/exclude options

Raised by sergeimorozov on the mailing list: https://groups.google.com/g/debezium/c/8R_IxaXFTGs. Specifically, it should be clarified that the provided regular expressions apply to the entire database/table/column names, i.e. they are implicitly anchored in regex terms. They don't find any matching stubstrings in those object names.