revamp TTS onboarding materials

[afeld]

Background Information

As part of TTS onboarding, new hires are sent through the self-directed Tech Portfolio TTS Class. They are asked to go through the following:

1. Infrastructure Best Practices
2. https://handbook.tts.gsa.gov/software/
3. https://handbook.tts.gsa.gov/collaboration-tools/
4. https://handbook.tts.gsa.gov/tools/slack/rules/
5. https://before-you-ship.18f.gov/security/
6. https://before-you-ship.18f.gov/infrastructure/
7. https://digital.gov/resources/an-introduction-github/
8. https://handbook.tts.gsa.gov/contributing/
9. Confirmation quiz

We should reconsider whether this is the right material to have them go through, or if anything's missing.

Implementation Steps

• [ ] Ask for #microrequests help
• [ ] Update Infrastructure Best Practices, which may be rewriting it or deleting it (in favor of content that exists elsewhere)
• [ ] Marge Infrastructure Best Practices into the Handbook
• [ ] Rewrite quiz

Acceptance Criteria

• [ ] Consensus in the Tech Portfolio that new hires are getting the appropriate information as it relates to things in our team's scope