Add support for complex accordion block with embeds

[ramboz]

some pages are using accordions with an embedded table.

The proposal is to extract each accordion content into a separate page. The accordion content would be a simple link to the .plain.html, and the accordion block would dynamically load this async as needed.

List:

• [x] https://www.delta.com/us/en/skymiles/medallion-program/international-partner-skyteam-benefits
• [x] https://www.delta.com/us/en/skymiles/medallion-program/medallion-upgrades
• [ ] https://www.delta.com/us/en/skymiles/program-resources/program-rules

[Dereje24]

Adding a page here: https://www.delta.com/us/en/skymiles/program-resources/program-rules