[feat] Add border-block-start custom props to <rh-tile>

[markcaron]

Description

Adding border-block-start custom props to <rh-tile> would allow us to handle a new trend we're seeing in mockups/designs.

Suggested solution

Per FED discussion, we'd add the following custom props:

• --rh-tile-border-block-start-width
• --rh-tile-border-block-start-color

Which then can be styled with some CSS in a pattern, like:

--rh-tile-border-block-start-color: var(--rh-color-accent-brand-on-light, #ee0000);
--rh-tile-border-block-start-width: var(--rh-border-width-lg, 3px);

Screenshots

Ignoring the Tile arrow in the heading, we're looking to be able to do something like this:

[markcaron]

Going with a different approach