Sort Runtime APIs alphabetically

Also I wonder if it's worth tweaking the sidebar to better separate them from the list of pallets, which is visually identical at the moment. Maybe add a `Pallets` title before the pallet stuff?

<img width="287" alt="Screenshot 2024-05-15 at 12 20 26" src="https://github.com/paritytech/subxt-explorer/assets/3799193/c6c379dd-cb5a-4d25-a20b-1de78c8f21e4">
