V6 support in Org

[evwilkin]

This epic will track any & all Org updates required to support V6 development, documentation, release workflows, etc.

### Infrastructure & workflow tasks
- [ ] https://github.com/patternfly/patternfly-org/issues/3835
- [ ] https://github.com/patternfly/patternfly-org/pull/3845

### Website styling/theming
- [ ] https://github.com/patternfly/patternfly-org/issues/3764
- [ ] https://github.com/patternfly/patternfly-org/issues/3756
- [ ] https://github.com/patternfly/patternfly-org/issues/3859
- [ ] https://github.com/patternfly/patternfly-org/issues/3877
- [ ] Add disclaimer to extensions pages about new styling in progress
- [ ] https://github.com/patternfly/patternfly-org/issues/3909
- [ ] https://github.com/patternfly/patternfly-org/issues/3910

[andrew-ronaldson]

For the short-term the Extensions section will be hidden from the Alpha staging site while we go through the list and make all the necessary uppates.. There are Epics tracking these from Design > Dev work

[andrew-ronaldson]

PR up for https://github.com/patternfly/patternfly-org/issues/3910