Update guide with canvas shortcut information

Author: tianlang0704

guides/README.md

@@ -226,6 +226,15 @@ function MyNode()
   this.addWidget("text","Surname","", { property: "surname"}); //this will modify the node.properties 
 }
 ```
+## LGraphCanvas
+LGraphCanvas is the class in charge of rendering/interaction with the nodes inside the browser.
+### Canvas Shortcuts
+* Space - Holding space key while moving the cursor moves the canvas around. It works when holding the mouse button down so it is easier to connect different nodes when the canvas gets too large.
+* Ctrl/Shift + Click - Add clicked node to selection.
+* Ctrl + A - Select all nodes
+* Ctrl + C/Ctrl + V - Copy and paste selected nodes, without maintaining the connection to the outputs of unselected nodes.
+* Ctrl + C/Ctrl + Shift + V - Copy and paste selected nodes, and maintaining the connection from the outputs of unselected nodes to the inputs of the newly pasted nodes.
+* Holding Shift and drag selected nodes - Move multiple selected nodes at the same time.
 
 # Execution Flow
 To execute a graph you must call ```graph.runStep()```.
@@ -320,11 +329,6 @@ this.setOutputData(0, {
 
 
 
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