Set first `api_version`

[MarcoGorelli]

Are we OK to:

• merge open non-draft PRs
• add a git tag 2023-07 (or 2023-08)

?

Then I can start upstreaming __dataframe_consortium_standard__ methods which defer to the dataframe-api-compat package (or at least, try to)

[MarcoGorelli]

as per today's discussion - once #223 is in, let's push a 2023-08-beta tag

Is there anything else that needs doing here for releases?

I've added a note to dataframe-api-compat saying to not rely on it for lazy computation just yet

[rgommers]

I can't think of other things. Please go ahead and push the tag @MarcoGorelli! You did most of the implementation work here, so I'd say you get to do the honours for tagging the first beta as well here:)