tools lessons (#1218)

* tools lessons

* updated summary

* more images

* wire up images

* fixing radio send-value

docs/projects/servo-calibrator.md

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+# Servo calibrator
+
+Use this program to calibrate the angles of a servo.
+Press ``A`` to reduce the angle by 5 and ``B`` to
+increase it by 5.
+
+The current angle is displayed on the screen
+in a loop.
+
+```blocks
+let angle = 90
+input.onButtonPressed(Button.A, () => {
+    angle = Math.max(0, angle - 5)
+    pins.servoWritePin(AnalogPin.P0, angle)
+    led.stopAnimation()
+})
+input.onButtonPressed(Button.B, () => {
+    angle = Math.min(180, angle + 5)
+    pins.servoWritePin(AnalogPin.P0, angle)
+    led.stopAnimation()
+})
+basic.forever(() => {
+    basic.showNumber(angle)    
+})
+pins.servoWritePin(AnalogPin.P0, angle)
+```