Manage job postings

[wesley-dean-gsa]

As a maintainer of the TTS and Join TTS websites, so that I don't need to enter job posting data twice, I would like some mechanism to allow me to only enter postings once and have them show up in both places.

### Tasks
- [ ] https://github.com/GSA-TTS/tts.gsa.gov/issues/166
- [ ] https://github.com/GSA-TTS/tts.gsa.gov/issues/167

[wesley-dean-gsa]

The plan is to consolidate both the TTS and Join TTS websites into one. Currently, the goal is to make this happen before we launch the new TTS website.

For several scheduling reasons, the website launch will be moved back from its current target (Wednesday, August 28th). Therefore, we'll need to figure this out in the near future.

One thought is to have both sites running concurrently. We would need to synchronize the job posting data from one repository to another. The most obvious way is to pull postings data from the Join TTS repository into the TTS website repository, potentially using a script or workflow.

[wesley-dean-gsa]

This supersedes #83

[wesley-dean-gsa]

To reiterate what I apparently lost earlier, the join repo will be going away, so we're migrating, not synchronizing.

[wesley-dean-gsa]

The job postings are back, as is the automated listing of positions based on the positions' pages.

[wesley-dean-gsa]

see #210 #211