[Accessibility] Posts block - Posts should be in a list

[andeng1106]

Describe the bug

• To be able to check this, try the WordPress Query Loop block as a sample block.

• When you add a Query Loop block, it uses the list tags:
  

• While Stackable Posts block uses div tags:
  

To Reproduce
Steps to reproduce the behavior:

1. Add a new page
2. Add a Posts block
3. Save page and view frontend
4. Inspect to see that Stackable uses div tags for each post list item

Expected behavior
Stackable Posts block should use list tags

Screenshots

Screen.Recording.2024-07-19.at.10.mp4