Show domain expertise for project team members

Why is this change being made?

As per the new code review process we are defaulting to assigning code reviews to domain experts. This change introduces a way for a team member to add domain expertise as well and for it to be listed on the engineering projects page.

How it works

Team members can define their domain expertise as follow:

1. Define a new or use an existing domain expertise located in data/domain_expertise.yml.
2. Update data/team.yml with a new domain_expertise property and list all domain expertise.

Example:

domain_expertise.yml

webpack:
  display_name: Webpack
  link: https://webpack.js.org/  
frontend_architecture:
  display_name: Frontend Architecture
  link: https://docs.gitlab.com/ee/development/fe_guide/architecture.html  

team.yml

domain_expertise:
    - webpack
    - frontend_architecture

This will then show up on the https://about.gitlab.com/handbook/engineering/projects/ page like this: