Documentation Updates (new user sections)

[vade]

This Issue continues the ongoing documentation work and is meant to capture new documentation to finish sections for the documentation refactor.

This is a bit of a call to action for the community.

• Guidance on the Pipeline Architect intro guide with language.
• Guidance on sample media to include with OTIO / OTIOD / OTIOZ files for users to base tutorials off of.
• Guidance on user facing tutorials. Can we make a set of tutorials which are lightweight introductions to common use cases for OTIO using the sample media and well known reference implementations?
• Roadmap needs attention if we want to include it

### Tasks
- [ ] Roadmap update
- [ ] Getting started tutorials

[jminor]

Sample OTIO + media suitable for tutorials can be found here:

• https://dpel.aswf.io/alab-trailer
• https://dpel.aswf.io/aws-picchu-edit
• https://github.com/darbyjohnston/otio-oc-examples