missing table footer functionality

[hhfiddelke]

Is your feature request related to a problem? Please describe.
I needed to insert a table footer. It was not available, so tried to insert it via source window, but the editor removed?/converted the tag to a tbody.

Describe the solution you'd like

1. Suneditor should not remove the standard tag from the source
2. There should be a functionality "AddTableFooter" similar to the "AddTableHeader"- function.

Describe alternatives you've considered
I was able to remove this behavior by adding "addTagsWhitelist":'tfoot', to the init- sequence. but i think this should be necessary.

Unfortunately are my JS- skills not the best 😥. So i hope it is only copying/add the "tfoot" to the "thead"- functionality in expressions, CSS and JS.