Move content-editable toolbar to workspace-tools and replace content editor with lexical.dev

[kof]

Currently the toolbar is still inside the canvas/iframe and now we moved outlines into workspace tools and they get rendered on top of the text editing toolbar

[okonet]

I'm thinking that in order to avoid all possible and uncovered edge cases like #77 we should not rely on content-editable at all. Instead, we could build a UI in the designer using the outline layer (since #56 is merged) and use props to pass down the children to components.

One gotcha could be, though, is modality of this UI but I think we could create a UX similar to content-editable although keeping it in a completely separate JS / DOM tree.

Additionally, I think it would be great to show children prop explicitly somehow in the advanced tab. This would solve two potential use cases: users can edit content in the side panel (consistently with styles), and it would allow editing non-children props like value in the <input type="button">.

WDYT?

[okonet]

You can take a look at https://docs.slatejs.org since its a similar abstraction like https://lexical.dev. But from my past experience https://prosemirror.net worked the best.

[kof]

Follow up issue #107