Add title to radio button columns

Re-rolling the patch in #8 to work with the latest version of this module (8.x-1.3).

Re-rolling the patch in #12 to work with the latest version of this module (8.x-1.3).

I have applied the patch and checked that User can set the Revision Table header by giving the column names in the "Revision overview column names" section in the "Diff General Settings".

This issue duplicates the work done in 🐛 Missing column headings in Revisions list Needs review

I do not think these need to be configurable.