Configuration option to set which version of Bootstrap is being used

Problem/Motivation

As issues #3380799: Module does not support Bootstrap v3 syntax for vertical tabs and #3377313: Tab is not working in Bootstrap 5 make evident, there is a need for this module to "know" which version of the Bootstrap framework a site is using, so that it can modify markup to fit the expectations of the version.

This information cannot be derived from *how* the framework is integrated in Drupal, since this module's approach is to support any implementation in a custom or contrib theme. Therefore, sites need to be able to define *for* this module which version is being used.

Proposed resolution

Provide a site-wide configuration option in a settings form that allows the site to set whether this module should render content to be compliant with Bootstrap 3, Bootstrap 4, or Bootstrap 5.

Once this configuration option is in place, #3380799: Module does not support Bootstrap v3 syntax for vertical tabs and #3377313: Tab is not working in Bootstrap 5 can be completed, with conditional logic to adjust as necessary to the Bootstrap framework version.