Show contributors list in the card and course pages

[svarlamov]

We should recognize course contributors (via GitHub/git blame) for the course and also for each piece of content.

@LanderMuruaga This would be an enhancement to the course UI update that we're working on now. Potentially we can implement this after that initial design is implemented.

@stanvarlamov This would require some updates to the GQL API and I will also need to update the ecosutil importer to fetch the contributors and then add them to mongo.

(WIP) Todos

• Create/finalize designs

• Update mongo data model

• Update eocsutil import routine

• Update gql server models/logic to pull fields

• Update GQL schema/resolvers

• Update web client to pull data from GQL

• Update web client UI based on designs

[LanderMuruaga]

Added contributor list into a sidebar module of Course detail.
I wont add them into course cards on Course list or Dashboard. It adds a lot of noise and I dont see it useful at this point.
In the course detail instead is really usegul, encouraging users to take part.

It could be shown in 2 ways.

1. Contributors + Edit in Git together in the same module (check the image for more info)
2. Contributors + Edit in Git in different modules, using them independently.