Usage:
Click on the grid to make a new node
Ctrl-click a node to do a Hadamard
Select a node, then shift-click another node to do a CZ
Press space to rotate the grid
API usage:
GET https://abv.peteshadbolt.co.uk/graph -> JSON
POST JSON -> https://abv.peteshadbolt.co.uk/graph
POST JSON -> https://abv.peteshadbolt.co.uk/edit
See here for docs.