On iOS the message is sent twice, with a duplicate event_id.
It cause error on logs, in different places (synapse, mautrix, ...)
It required to fix the already existing json or reimport the stickers.
The "packs/scalar*" example already include this field, and it works.
The license was initially MPLv2 as I expected the project to be a fairly
simple tiny web app, but it has already grown into multiple files. Now
that I'm going to add a server component, I'm switching the license for
future versions to AGPL like all my other non-library projects.
