Automatic workspace folders in chrome dev tools

[siddhantk232]

https://chromium.googlesource.com/devtools/devtools-frontend/+/main/docs/ecosystem/automatic_workspace_folders.md

fastn can serve the well-known json which should hopefully allow devs to edit .ftd files from dev tools and have them persisted on disk. This is helpful during debugging.

other things that can make this more awesome:

• hot code reloading of .ftd files
• fswatcher that reloads on file change (even FASTN.ftd!)