Add epitope coloring for existing pathogens

[joverlee521]

Brought up on Slack:

it would be nice if we just counted mutations for surface proteins as a basic standard coloring. The same way we do with https://nextstrain.org/ncov/open/global/all-time?c=S1_mutations.

TODOs

Add pathogen to list here or create issue in pathogen repo and link as sub-issue

• norovirus
• seasonal cov
• rsv G protein