Add "Unsupported in PL/SQL Cop Validators" explanation and usage

[kibeha]

I like this additional property! 👍

Originally posted by @PhilippSalvisberg in #86 (comment)

[kibeha]

!!! missing "Unsupported in PL/SQL Cop Validators" should be added to introduction.md. Probably not under "Severity of the rule". Maybe an addition chapter.

The following rules are currently not supported by a PL/SQL Cop validator:

G-3160 (cannot identify type of a column)
G-5010 (cannot identify logging framework and where it should be applied)
G-8410 (cannot identify where an application lock would make sense)
G-8510 (cannot know where the use of application_info is sensible)
They should be tagged with "!!! missing "Unsupported in PL/SQL Cop Validators"

[PhilippSalvisberg]

I missed the G-3170 in the previous list. Guidelines without a validator check are documented here https://github.com/Trivadis/plsql-cop-cli/blob/main/validator-limitations.md#guidelines (incl. the reason).

[kibeha]

Thanks for the link, very helpful 👍