Nostrscript is the thing @jb55 used to brag about which eventually became nostrdb (I think). AFAIK a spec or library was never published. I also played around with a lua scripting language:

GitHub

GitHub - coracle-social/ostrich-script-js: OstrichScript is a convention for extending nostr clients with user-defined functionality.

OstrichScript is a convention for extending nostr clients with user-defined functionality. - coracle-social/ostrich-script-js