youtube short videos for numaflow tutorials

[vigith]

Summary

Today, users are not aware of what a Numaflow pipeline is or the different types of vertices, and how they are integrated.

The best way to introduce Numaflow could be through a short set of tutorial videos.

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Message from the maintainers:

If you wish to see this enhancement implemented please add a 👍 reaction to this issue! We often sort issues this way to know what to prioritize.

### Tasks
- [ ] Anatomy of a pipeline tutorial
- [ ] high level architecture (what does each container do)
- [ ] Source Vertex and Source Transformer tutorial
- [ ] Sink and optional Fallback tutorial
- [ ] Map Tutorial
- [ ] how to write a UDF
- [ ] setup a local pipeline for testing
- [ ] Reduce Tutorial