Improve components documentation

[saemideluxe]

The documentation for the components could be improved a lot by adding parts of the carbon documentation directly into the docstrings. Also, extending the widgetpreview to include more components would be nice.

• bread.layout.components.button
• bread.layout.components.content_switcher
• bread.layout.components.datatable
• bread.layout.components.forms # present on widget preview, but docstrings for widgets not complete?
• bread.layout.components.grid
• bread.layout.components.icon
• bread.layout.components.loading
• bread.layout.components.modal
• bread.layout.components.notification
• bread.layout.components.overflow_menu
• bread.layout.components.pagination
• bread.layout.components.progress_indicator
• bread.layout.components.search
• bread.layout.components.shell_header # this is complicated and not very standardized anyway, ignoring
• bread.layout.components.sidenav
• bread.layout.components.tabs
• bread.layout.components.tag
• bread.layout.components.toggle
• bread.layout.components.tooltip