document geb, selenium and testcontainers changes

[jamesfredley]

No description provided.

[jamesfredley]

@matrei @sbglasius @jdaugherty I'd recommend putting these documentation changes on #929, since it has a ton of other changes for Grails 7.0.0-M1.

[matrei]

I'd recommend putting these documentation changes on #929, since it has a ton of other changes for Grails 7.0.0-M1.

@jamesfredley Roger that!

[jdaugherty]

A lot of the documentation has already been done in the README.md of the geb project. We just need to move it there. @matrei did you want to do this or should I?

[matrei]

@jdaugherty If you have the cycles available, please go ahead. Otherwise, I will try to find time this evening.

[jamesfredley]

I think the biggest thing is that users will need a container environment. Might be worth putting something about that in https://github.com/grails/grails-doc/pull/929/files#diff-a274b28b31934a59d9b250f2ff145b5dc95e9a30ba91df2bf3d970853c324aa7

[matrei]

New section added in "What's new": https://github.com/grails/grails-doc/pull/929/files#diff-a274b28b31934a59d9b250f2ff145b5dc95e9a30ba91df2bf3d970853c324aa7

Reviews welcome!

[jamesfredley]

@matrei It looks good.

I am going to work through the restoration of the older grails command docs, so I will take care of the sections related to grails-forge cli features.

functionalTesting.adoc and integrationTesting.adoc are the other remaining location with Geb details.