Add visualization entry point for observable notebooks

[guerler]

Exploring the option to integrate observable notebooks into Galaxy. Thank you for the suggestion @nekrut.

How to test the changes?

(Select all options that apply)

• [ ] I've included appropriate automated tests.
• [ ] This is a refactoring of components with existing test coverage.
• [ ] Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• [x] I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[nekrut]

Based on discussion with @dannon : we can make all tabular datasets below certain size (e.g., 1 Mb) to be visualizable in a boilerplate notebook that is specifically designed for visualization of of tsv (or csv) data: https://observablehq.com/d/865ef797f8cf2cd8

[d-callan]

ok so on the one hand this is pretty cool..

but also, some practical questions, if i may:

1. are notebooks allowed to live anywhere? or is there a galaxyproject observable org as well?
2. in either case, what does dev and maintenance look like? if they live anywhere, then i worry about forking of forks etc to fix minor bugs or add features. if they live in a dedicated org, does that make it harder for others to potentially contribute?
3. do we care that code that lives in observable doesnt have a good means that i know of to introduce unit tests, linting etc? idk how much we depend on these types of things in other context..
4. are we embedding the entire notebook? like all cells, even if all theyre doing is importing some dependency?