Refactor `BlogsList` component, so that it can be used within any page layout

[olayway]

From our docs page:

The BlogsList component requires a simple page layout, which you need to specify in the frontmatter of your blogs index.md page.

Acceptance

• [ ] @flowershow/core's BlogsList component can be used in any layout and look good (= it is responsive)

Tasks

• [ ] adjust styling of the BlogsList component to make it responsive and independent of any styles currently applied by the Simple layout (which is required atm to make the BlogsList component look good)