docs(Masthead): update demo to be fullscreen

[tompsota]

What: Closes #7210

[patternfly-build]

Preview: https://patternfly-react-pr-7928.surge.sh

A11y report: https://patternfly-react-pr-7928-a11y.surge.sh

[nicolethoen]

After talking with @mattnolting and @mcarrano, this demo should be renamed to "Masthead with utilities and user dropdown menu". It might also help to add a few sentences below the title that explains some of the design and implementation details. Possibly something like:

Many mastheads contain utilities which collapse into a dropdown at smaller view port widths. These utilities could include a notification badge to open and close a notification drawer, a link to app or user settings, a help icon which could launch quick starts or link to other resources, and many other utilities. In this demo, the notification badge does not collapse down into the mobile menu so that it is always visible even at narrower view port widths.

Additionally this demo needs to include building the masthead itself so consumers can see how it's done. It shouldn't use the DashboardWrapper.

[tompsota]

Good catch @mcarrano! Should be fine now.