How to guide for developing nbdev

_aka "runs with scissors"_

Document how to develop and test with pre-release versions of nbdev and the primary dependencies (i.e. quarto, jupyter), all of which are actively being developed.

Some topics to potentially include:

- Describe how to preview locally using a prerelease version of nbdev (head or a particular commit)

For example:
```
pip install -U git+https://github.com/fastai/nbdev.git@08462b3da90c86a06cd62159babc69c346d21f88
```

- Describe how to deploy to GitHub using a prerelease version of nbdev and/or quarto

workflows/deploy.yaml
```
jobs:
deploy:
runs-on: ubuntu-latest
steps:
- uses: fastai/workflows/quarto-ghp@master
with: {pre: 1}
```