Watch Mode

[David]

Description

Here is the use case:

You want to regenerate the openapi types when a file has changed (in this case the openapi.json file).

It would be interesting to have a sort of watch mode built-in which would check changes to the openapi json file (or however is the best way to do this).

For inspiration/extra examples other packages have done something similar like this: https://the-guild.dev/graphql/codegen/docs/getting-started/development-workflow#watch-mode.