Updating the Revenue total

Currently the front page figure, "Revenue £10.3m", is hard coded:

• https://git.coop/cotech/website/blob/master/index.html#L24

On the old WordPress version of the site each co-op could enter a (private) figure and the totaly was generated from the sum.

Do we want to:

1. Manually keep track of this total and if so how?
2. Have a (public) field for each co-op to enter their revenue for the year (most co-ops will have to make their accounts public in any case, so this won't be private data?) and then add them all together?