feat(showcase): add multi-player showcase

[jboix]

Description

Resolves #3 by introducing a new showcase that displays multiple players on the same page. A button has been added to allow the user to toggle the mute state for both players.

[!Note] Only one player can have active tracking at a time, an issue has been created to provide documentation for this limitation, see: SRGSSR/pillarbox-web#208.

Changes made

• Updated the titles of all pages in the application to follow a consistent pattern.
• Updated the text example of the start-time showcase, the showcase itself was working but the text was still displaying the broken urn.

[amtins]

I also noticed a small bug when hovering over the player controls.

[jboix]

I also noticed a small bug when hovering over the player controls.

This has been fixed too.