Start a 9.1.x branch for Varbase Media to support Bootstrap 5

Problem/Motivation

#3229295: Initialize Varbase Theme (Bootstrap 5 - SASS) theme ( Vartheme BS5 )
#3251531: Start a 9.1.x branch for Varbase and Varbase Project to support Bootstrap 5

Looking at the Migrating to v5. The Bootstrap 5 has many logical changes.
A new branch is logical. To have a space for development and space for update and migration path from Bootstrap 4 to Bootstrap 5

Breaking

Responsive embed helpers have been renamed to ratio helpers with new class names and improved behaviors, as well as a helpful CSS variable.

• Classes have been renamed to change by to x in the aspect ratio. For example, .ratio-16by9 is now .ratio-16x9.
• We’ve dropped the .embed-responsive-item and element group selector in favor of a simpler .ratio > * selector. No more class is needed, and the ratio helper now works with any HTML element.
• The $embed-responsive-aspect-ratios Sass map has been renamed to $aspect-ratios and its values have been simplified to include the class name and the percentage as the key: value pair.
• CSS variables are now generated and included for each value in the Sass map. Modify the --bs-aspect-ratio variable on the .ratio to create any custom aspect ratio.

Breaking

Dropped the .media component as it can be easily replicated with utilities. See #28265 and the flex utilities page for an example.

Proposed resolution

• Start a 9.1.x branch for Varbase Media
• #3252753: Add the screen xl-max and screen xxl-min to Varbase Media breakpoints
• Changed the following in configs and logic
  • From embed-responsive to ratio
  • From embed-responsive embed-responsive-1by1 to ratio ratio-1x1
  • From embed-responsive embed-responsive-16by9 to ratio ratio-16x9
  • From embed-responsive embed-responsive-4by3 to ratio ratio-4x3
  • From embed-responsive embed-responsive-21by9 to ratio ratio-21by9

Remaining tasks

• ✅ File an issue about this project
• ✅ Start a 9.1.x branch
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ Update Release Notes and Update Helper on new feature change/addition
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Release varbase-10.0.0-alpha1, varbase_media-9.1.0-beta1

Varbase update type:

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A