Add people & content to the People page

[robyngit]

The content/people directory has information for every person who has ever been a speaker for a webinar. If the person is also part of DataONE, then they are listed automatically on the new People index page. We still need to add a markdown file for each person who is part of DataONE but hasn't given a webinar.

To automatically list team members on the People page, the person must have a value for the d1_team parameter in their markdown file (e.g. d1_team: Leadership team). This value must match one of the team names listed in people/_index.md file under d1_teams. Add more values to d1_teams if needed.

In addition, the title, description, and content of the Team/People page should be updated.

[robyngit]

This is a duplicate of #41