Support adding images to slides

[pscanf]

As discussed in #6, support adding image to slides.

[hydrosquall]

👋

• Image support was added to Excalidraw in this PR feat: image support excalidraw/excalidraw#4011
• This feature was included in the public API as of v0.11.0 https://github.com/excalidraw/excalidraw/releases/tag/v0.11.0

I am optimistic that adding support for this will involve upgrading

https://github.com/excalideck/excalideck/blob/master/packages/excalideck-editor/package.json#L24

to

0.11.0

However, since there are breaking API changes in this release, it's possible a few more steps might be needed.

[pscanf]

Hey @hydrosquall. Sorry for the late reply. Yes, indeed versions after v0.11.0 have that feature. Unfortunately, as you mention, there are breaking changes in the API* which makes it not immediate to upgrade.

I have it in the back of my mind to upgrade, but unfortunately I haven't had the time/need to work on this project for a long time. (Contributions are of course welcome. 🙂 )

• IIRC, one of the main APIs to get the drawing data becomes async - which means that all Excalideck functions using that API need to become async as well - and the format of the drawing changes slightly to support the inclusion of images.