Create a webhook triggering the update route of ESGVOC Backend

[SebastienGardoll]

General Issue

ESGVOC Backend runs in background processes that expose the functions of the ESGVOC library. As vocabularies evolve, ESGVOC Backend has to be updated accordingly. I propose to create a webhook for every vocabulary repository (and for every ESGVOC Backend instance) which triggers the update route of ESGVOC Backend (POST) on every push. A special care must be taken with the webhook secret.