add a test of rainbows

tests/circuitpython/rainbows.py

@@ -0,0 +1,6 @@
+import rainbowio
+
+for i in range(0, 256, 15):
+    print("{:3} {:06x} {:06x}".format(i, rainbowio.colorwheel(i), rainbowio.colorwheel(float(i))))
+for i in range(256, 1024, 128):
+    print("{:3} {:06x}".format(i, rainbowio.colorwheel(i)))

tests/circuitpython/rainbows.py.exp

@@ -0,0 +1,24 @@
+  0 ff0000 ff0000
+ 15 d22d00 d22d00
+ 30 a55a00 a55a00
+ 45 788700 788700
+ 60 4bb400 4bb400
+ 75 1ee100 1ee100
+ 90 00f00f 00f00f
+105 00c33c 00c33c
+120 009669 009669
+135 006996 006996
+150 003cc3 003cc3
+165 000ff0 000ff0
+180 1e00e1 1e00e1
+195 4b00b4 4b00b4
+210 780087 780087
+225 a5005a a5005a
+240 d2002d d2002d
+255 ff0000 ff0000
+256 ff0000
+384 007e81
+512 ff0000
+640 007e81
+768 ff0000
+896 007e81