Airtable: Show Client registration status as percentage and colour

Need: Quick reference - how are we doing for registrations?

Solution: New column added with visual representation and percentage of registrations completed.

Note: only applies to upcoming cohorts to inform ops when herding the cats coming up to the first session.

Here are the values for the colors: 

 <= 50, "🔴",   <= 80, "🟠",  <= 99, "🟡",  = 100, "🟢"