[Tagging] Feature Proposal - RFC - Blood donation 2

[Ruben Maes]

After the proposal Donation was rejected, I tried to address the
issues that were raised in a new proposal using
healthcare=blood_donation:

https://wiki.openstreetmap.org/wiki/Proposed_features/Blood_donation_2

You are of course welcome to point out any flaws.
You are also welcome to improve the language if you like: make phrases
more fluent, fix mistakes, etc.

Kind regards
Ruben