Create sim primer

[arouinfar]

Tracking sim primer publication in this issue, so that #50 can be closed.

[arouinfar]

Marking as on-hold until the following primers are published:

• [x] https://github.com/phetsims/circuit-construction-kit-dc/issues/167
• [x] https://github.com/phetsims/circuit-construction-kit-dc-virtual-lab/issues/10
• [x] https://github.com/phetsims/projectile-motion/issues/147
• [x] https://github.com/phetsims/pendulum-lab/issues/191
• [ ] https://github.com/phetsims/capacitor-lab-basics/issues/235
• [x] https://github.com/phetsims/hookes-law/issues/44
• [ ] https://github.com/phetsims/gravity-and-orbits/issues/260

[arouinfar]

• [x] Draft script - 5/23/18
• [x] Record rough version for script verification - 5/30/18
• [x] Review script verification draft, and adjust script as necessary - 6/1/18
• [x] Record another draft 6/6/18
• [ ] Review 2nd draft
• [x] Produce primer and upload
• [x] Caption primer

[arouinfar]

The primer is now live, closing.