Feature/frame node

[mokaddem]

Hi @jerosoler!

One again, thanks for this really cool project!

I started to have complex flows and thought it would make sense to organize nodes by grouping them together. Hence, the introduction of "Frame nodes".

Here is how you can use it

const frameNode = {
    nodes: [4, 5],
    text: "Frame node with a text",
    class: "custom-framenode-class",
}
editor.addFrameNode(frameNode)

Along with an screenshot

Apologies in advance that this PR requires #687 to be merged before (you can still cherry-pick if you want).
Anyway, let me know if you'd like me to change something for it to be merged.

Cheers

[jerosoler]

Hi!

@mokaddem thanks! for PR.
Looks good! I'll take a look at it.

🎉🎉

[converseKarl]

Jero this looks good and you should definitely merge this in for the community.