Standardize certificate creation process

[angela-li]

I believe @emdodwell did this for NYC, we should make it easy for folks to do so for any workshops they organize themselves (possibly include it in an organizing workshops guide)

[hturner]

This is implemented in the fwdbrand package: https://github.com/forwards/fwdbrand. The current template is specific to Forwards though, and there are a couple of merge requests waiting. This would be a good thing to get on top of at the Forwards meeting in Toulouse and I have added it to the agenda (https://docs.google.com/document/d/1rYzWkjhyPH86SHnMJGyJcx-jBB_vnJ6C_EN7iUx4xpw/edit)

I like the idea to add this to a workshop organizers guide.