Presenter/Speaker profiles

Expand functionality to allow a searchable list of presenters/speakers. Profile info could be stored in a `speakers.yaml` file and linked to presentations on the GH username.

"Cloud Native certified" speakers could be tagged that way to separate them from everyone else who just submits a presentation. "Cloud Native certified" speakers are basically the equivalent of the speakers we used to accept in the Speakers Bureau. It is those who have certain credentials to make them good candidates for inviting to a conference to speak.

Other tags could be used to designate "staff" presentations or speakers from CNCF.