Provide script to validate XML against ADR

[cspray]

It is possible, and even likely, that a developer will implement an ADR and then forget to run the command to regenerate the corresponding XML. We should provide a script that validates the number and titles of records stored in XML match against what's in the codebase. On success it should exit 0 with no output, if it fails it should exit 1 with a list of which ADR are missing.