Create catalog of progress tracking cards

[maherou]

PSIP uses progress tracking cards (PTCs) as a way to articulate steps and track progress toward improvement of identified productivity and sustainability goals. To assist teams and mentors, we should have a collection of sample PTCs in the PSIP-Tools repo.

[maherou]

I have added a new page describing the goals and outlines for creating PTCs. I have also uploaded three sample cards. More can be added, but this should be a reasonable starting point. @bernhold, please let me know if this current version is a good enough starting point.