Improve docs copy/watch handling

[knolleary]

Recent changes around the netlify part of the website build meant running the build locally didn't always generate all of the product docs.

I believe this was due to a timing issue around the copy_docs script running in parallel to 11ty starting up - a timing issue that was exposed by removing the netlify part of the build.

This PR modifies how the copy_docs/watch_docs scripts operate so that:

1. copy_docs can be run once before 11ty is started
2. a new watch mode in copy_docs can be used in parallel to 11ty starting. This only copies things over when changes are made - it does not do an initial copy over.

To achieve this, I've scrapped the watch_docs script that used nodemon - it was a sledgehammer that would copy the full docs tree over on every change - leading 11ty to rebuild far more than it needed it.

The new watch mode handles individual file changes and only copies/creates/deletes files that have changed.

This is working well locally - but will appreciate some local testing by others before merging.

I haven't (yet) touched the blueprint copy/watch scripts, but if this approach works well for core docs, I'll refactor those scripts to reuse what I've done here.

[ZJvandeWeg]

Naive first question: what happens if we just symlink the docs directory?

[joepavitt]

what happens if we just symlink the docs directory?

Probably fine locally, but not sure that's a solution for the GH automation?

[ZJvandeWeg]

I assume that's fine @joepavitt, it's just a linux machine in an Azure DC. But the docs.json wouldn't be in the directory. Maybe we need to move that upstream?

[knolleary]

The copy of files does more than just copy the raw file - it rewrites the yml header to include additional meta-data. So a symlink wouldn't be appropriate. It also wouldn't work with the netlify build as I understand it.

The GH Action doesn't actually build the website - it does all the file copies then checks in the result to the live branch. This is the branch that netlify watches and pulls from then runs the build without having to run the doc copying because all the files are present in that branch already.

See https://github.com/FlowFuse/website/blob/main/.github/workflows/build.yml for reference