Fixes #22
Closes #75

Co-authored-by: Nischay <hegdenischay@gmail.com>

(and possibly break it on other browsers)

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.

Fixes UnicodeEncodeError with Windows 10 when trying to import sticker packs caused by the default encoding scheme in Windows

Show sticker body in hover tooltip

Rename import.py, since import is a keyword

    from sticker.import import cmd
                 ^
SyntaxError: invalid syntax

Fixes https://github.com/maunium/stickerpicker/issues/27.

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.