feat: add context menu to animations

[TrySound]

Now user can copy and paste specific animations between animation groups.

[kof]

Works great, I would suggest 2 improvements:

1. ability to copy all animations, similar to how we have it in advanced section, so this way if I have many animations, I don't have to copy them 1 by one. Call it "Paste animations" - this works for one or many

2. Add meta to the json similar to what we have on the instance: "@webstudio/instance/v0.1", so its easier to identify what this is and we can also version it if we need a schema change at some point

[kof]

this schema would be great: {'@webstudio/animation/v0.1': Array<Animation> }

[TrySound]

I don't think versioning is important for small short term copy paste here

[kof]

I don't think versioning is important for small short term copy paste here

Yeah, we don't know, still nicer to have a consistent structure with an identifier

[kof]

Works well, lets release!

[kof]

Interesting thing I noticed is that description is part of the object:
{"@webstudio/animation/v0.1":[{"name":"Video Ranges","description":"Fade in the element as it scrolls into view.","keyframes":[{"offset":0,"styles":{"opacity":{"type":"unit","unit":"number","value":0}}}],"timing":{"easing":"linear","fill":"backwards","rangeStart":["cover",{"type":"unit","value":0,"unit":"%"}],"rangeEnd":["cover",{"type":"unit","value":100,"unit":"%"}]}}]}