[Feature Request] Expand description of parachain lease extension using existing paraid

[paullallier]

The section of the wiki on Lease Extension with Non-Overlapping Slots Is quite short current, and led me to assume that I could only bid on an extension with the existing paraid, once the auction for leases starting after the end of the current slot had started.

As I result, I set up a new paraid and bid with it - at which point I realised there was a better option (I could have bid for a lease starting later than default).

I think this section would benefits for a slight extension - possibly with a screenshot - noting that you can bid for a section of the lease starting later than the earliest period the slot could cover?

Hopefully that makes sense?