Cookbook example of extra-expanded years

[ptomato]

Follow up from #240, we need a cookbook example that does this:

Create a Temporal derivative that supports arbitrarily-large years (e.g., +635427810-02-02) for astronomical purposes, ideally without requiring modifications to year-agnostic interfaces such as Time (but still supporting e.g. UnlimitedTemporal.Time.from("10:23").withDate("+635427810-02-02")).

A custom calendar seems a likely way to implement this.

[ryzokuken]

I suppose this is blocked on #638 for the time-being?

[ptomato]

Cookbook example to be written after the freeze and before Stage 3

[ptomato]

On further reflection this isn't a requirement for Stage 3. To be done later.