Support format oas3 in addition to oas3.1?

[DawMatt]

The current ruleset includes support for format oas3.1 but not oas3.

A superficial check of the changes ( https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0 ) and the ruleset indicates it doesn't make use of any OAS 3.1 specific features. In particular:

• the changes to the content definitions for requestBody do not appear to be relevant to the defined aliases
• given ... then statements within rules also don't appear to rely upon OAS 3.1 specific changes

Can we please add oas3 to the supported formats list? i.e.

formats:
  - oas3.1
  - oas3

I've already changed this in a local copy of the ruleset and it appears to be working OK.