[Enhancement] Move node to another node

[Quorafind]

Move node to another node to make the former node becomes children node of the latter.

like:

# google 

google is a company

# bing

blablabla

I move the google node on the mindmap to bing node. Then the text comes to:

# bing

blablabla

## google

google is a company

It would be helpful when I want to change the hypotaxis of them