Add official VintageStory Format Support, drop community made one

[tyronx]

Hey, official Vintage story guy here. Since some of our teams now start using Blockbench we've decided to become the official maintainer of this plugin, hence I propose to also remove the outdated community provided plugin in the same PR. This has been agreed upon by its 2 authors, codename_b (Anego Studios Team member) and DarkLuke1111 (VS community contributor), but i haven't contacted the author of the old plugin.

This version fully supports animation, as well as different animation interpolation modes.

I ran the validator, fixed some issues, but I'm afraid I don't understand how to fix this issue:
Metadata mismatch: "about" is set to undefined in plugins.json and "A Blockbench plugin that adds support for Vintage Story models" in JS file

When I add an about section of the plugins.json then the error changes that this should be in the about.md, which already exists.

This PR would also obsolete #460

[JannisX11]

Cool, I think people will be excited to have this available in the built-in plugin browser.

@Malik12tree for visibility on the unofficial plugin being replaced, I don't think there should be any concerns about that.

Some feedback from testing the plugin:

• Regarding the validation message: In BBPlugin.register it sets the about field to the package description. About is the text in the about.md markdown file, so it shouldn't be set at all in the plugin JS file.
• When first installing the plugin, it asks multiple times for file system access. I would recommend bundling that into one request, or only requesting once it's being used, for a better user experience
• The Vintage Story model format does not have a proper icon. So set a custom image as an icon you can create an image element via new Image().
• Not required, but having some info about the format when selecting it on the start screen would be nice

[tyronx]

Sorry about the close/reopen due to my weak Git-fu but looks correctly rebased now. It should now validate fully, ask for permissions only once and have an icon 👍

We also fixed 2-3 bugs in the plugin itself.