curate examples extensively

docs/code/edge.js

@@ -1,4 +1,4 @@
-// simple directed edge
+// A curved line going from the upper left to the lower right. The left side of the line has a red arrow facing left and the right side has a blue arrow facing right. Both arrows are triangular with black borders.
 let edge = Edge([0.2, 0.3], [0.8, 0.7], {
   arrow_beg: true, arrow_end: true, arrow_base: true,
   arrow_beg_fill: '#ff0d57', arrow_end_fill: '#1e88e5',

docs/code/network.js

@@ -1,4 +1,4 @@
-// simple network
+// A network with a node on the left saying "hello world" and two nodes on the right saying "hello" and "world". There are arrows going from the left node to each of the right nodes. The nodes have gray backgrounds and rounded corners.
 return Network([
   ['A', ['hello', 'world'], [0.25 , 0.5], 0.15],
   ['B', 'hello', [0.8, 0.25]],

docs/code/node.js

@@ -1,4 +1,4 @@
-// simple greeting
+// Two boxes with text in them that have black borders and gray interiors. The box in the upper left says "hello" and the box in the lower right says "world!".
 let hello = Node('hello', {fill: '#EEE'});
 let world = Node('world!', {fill: '#EEE'});
 let scat = Points([