Documentation Updates (new user sections)

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

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

No files or tests are identified in the issue. Review the existing Pipeline Architect introduction, documentation refactor sections, sample-media guidance, user-facing tutorials, and roadmap; done means completing the Roadmap update and Getting started tutorials tasks.

Written by the indexing model from the issue text.