[Component] Dotcom shell

[oliviaflory]

Dotcom Shell

• Depends on Masthead v2 (AEM)
• Depends on Footer

Acceptance criteria

For all components, some basic acceptance criteria should be observed when working on them:

• also update React wrapper
• update Storybook docs
• use visual design checklist before opening a PR (with emphasis on numbers 1, 2, and 6)
• update migration guide if necessary (here is a good example of how the guide could look)
• update unit tests where necessary (tracked in [Components]: Update @carbon/ibmdotcom-web-components v2 unit tests Epic #10369)
• Note: Currently there is no standardization of tests, duplicate and/or redundant tests, and inconsistency in UI testing. The team consensus is to modify the tests as necessary (markup/name changes, etc) but to give this lower priority if it becomes a blocker in completing a particular component. The tests will get an overhaul in the future, so it is unnecessary to get them completely updated.