* Allow dropping images into notebook to create attachments
Fixes#157577
This allows you to drag and drop image files or image data into a notebook cell to create an attachment
As part of this work, I also updated the paste attachment logic so that we can:
- Create multiple attachments in a single operation
- Create attachments of other mime types besides `image/png`
- Create attachments for images that have spaces in the filename
* Also allow pasting uri lists to create attachments
* Fix indent
* Add id
* Move attachment out of custom metadata, prep for attachment clean up in diff editor
* recover attachments from dirty notebook document
* Allow metadata to be restored when content changed/reverted in nb diff editor
* change dir of cellAttachmentRenderer
* add new directories to `.vscodeignore`
* add the .js directories back in...
* hopefully now understanding `.vscodeignore`