Move an existing doc into another doc

[virgile-dev]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
For now, you cannot move a sub-document from the pinned document bar. It is not always easy to drag and drop one document into another if they already exist, as they are sorted by their update date.

Describe the solution you'd like
I'd like to have a modal where I can easily move a document by searching it much like there is for drive

Describe alternatives you've considered
To move both documents to the top, make a small edit (bold, add a block) to both documents. Then wait a minute for the save to take effect and refresh your document list. Both documents will be at the top.

Discovery, Documentation, Adoption, Migration Strategy
If you can, explain how users will be able to use this and possibly write out some documentation (if applicable).
Maybe add a screenshot or design?

Do you want to work on it through a Pull Request?