How hot-reload for MD files is implemented in Contentlayer

[olayway]

Acceptance

• find out how hot-reload for MD files is implemented in contentlayer

Notes

Summary

• when contentlayer is run in development mode:
  • contentlayer config file is read and esbuild watch mode is used to watch for any changes to it
  • then, config values read from the file are used to generate the output .contentlayer/generated folder, but also, along the way, the content folder starts being watched for any changes using Chokidar

More info here:
https://github.com/datopian/flowershow/blob/main/site/content/notes/markdown-hot-reload.md

[olayway]

@rufuspollock I've added some notes here https://raw.githubusercontent.com/datopian/flowershow/main/site/content/notes/markdown-hot-reload.md
The summary is also in the issue description.

[rufuspollock]

@olayway any recommendation on whether we could reuse this in flowershow - note here i think this would be less a "built-in" and more a "howto" to start with.

[mohamedsalem401]

FIXED. #620