DashboardWrapper: codesandbox export error

[kmcfaul]

Current the DashboardWrapper / DashboardHeader / etc reused by full page demos do not import to codesandbox correctly.

We should either update the codesandbox export template to include these files (for every export, or looking through the code for import statements and conditionally importing) or copy the content of files into the example file as a separate class, effectively locally importing the wrapper. The latter has the downside of duplicating the code again, but maybe an upside of allowing a user to view the wrapper code without having to find the file in the codebase or looking at Page docs.

[evwilkin]

Related to https://github.com/patternfly/patternfly-org/issues/2737 & https://github.com/patternfly/patternfly-org/issues/2705