Organize examples

[bryannho]

Closes #100

• Reorganizes doc/examples so that each example goes by framework/example-name
• Removed Dockerfile for examples which no longer need it, ie. Solara (previously those frameworks needed to be deployed as Docker apps but now we support them natively)
• Once this is merged, will open a PR to cloud-frontend to update the locations of a few example apps. Once that is merged, will open another PR to doc to delete the old examples that were moved

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📚 Documentation preview 📚: https://ploomber-doc--126.org.readthedocs.build/en/126/

[bryannho]

@edublancas ready for review

Moved most of the examples out of the Docker folder, and into a folder for their own framework, ie. examples/docker/example-name -> examples/framework/example-name.

Removed Dockerfile from projects that no longer need it. Made sure those which had Dockerfiles removed will still deploy correctly (had to edit/create a requirements.txt for those apps)

The only app for which I couldn't remove the Dockerfile for was solara/keyword-extraction, because it requires some additional commands to be run in the Dockerfile (apart from just installing the requirements).

[edublancas]

let's remove this file (i guess there's another copy as well). this shouldn't've been merged so let's get rid of it)

this is from some old example

[bryannho]

Deleted this file and its copy