Add some 'infrared' api docs (#326)

* Add some 'infrared' api docs

* Fix display messages

* Change discussion of distance to relative

* Include motor speed note

libs/infrared-sensor/docs/reference/sensors/infrared.md

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+# Infrared sensor
+
+```cards
+sensors.infraredSensor1.onEvent(null, function () {});
+sensors.infraredSensor1.pauseUntil(null);
+sensors.infraredSensor1.proximity();
+```
+
+## See Also
+
+[on event](/reference/sensors/infrared/on-event),
+[pause until](/reference/sensors/infrared/pause-until),
+[proximity](/reference/sensors/infrared/proximity)

libs/infrared-sensor/docs/reference/sensors/infrared/on-event.md

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+# on Event
+
+Run some code when an object is detected by the infrared sensor.
+
+```sig
+sensors.infraredSensor4.onEvent(InfraredSensorEvent.ObjectNear, function () {});
+```
+
+How an object is detected depends on the light _thresholds_ set for the sensor. A threshold is a number for relative distance of the a return of reflected infrared light. The brighter the light, the nearer the object is. The value for what _near_ means is determined by this threshold. A certain minimum amount of light returned is also set to determine that an object is detected. The two thresholds you can set are:
+
+* **near**: a distance to set to detect objects coming close
+* **detected**: the brightness of infrared light to needed to detect presence of another infrared transmitter.
+
+## Parameters
+
+* **event**: the object detection action to wait for. The detection types (events) are:
+> * ``detected``: some other object is sending out infrared light
+> * ``near``: the sensor detected something within the distance of the near threshold
+* **body**: the code you want to run when something is detected by infrared sensor.
+
+## Example
+
+When the ultrasonic sensor on port 4 detects a near object, display its distance on the screen.
+
+```blocks
+sensors.infraredSensor4.onEvent(InfraredSensorEvent.ObjectNear, function () {
+    brick.showString("Object detected at:", 1)
+    brick.showNumber(sensors.infraredSensor4.proximity(), 2)
+    brick.showString("percent of range", 3)
+})
+```
+
+## See also
+
+[pause until](/reference/sensors/infrared/pause-until)

libs/infrared-sensor/docs/reference/sensors/infrared/pause-until.md

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+# pause Until
+
+Make your program wait until an some object is detected in proximity of the infrared sensor.
+
+```sig
+sensors.infraredSensor1.pauseUntil(InfraredSensorEvent.ObjectDetected);
+```
+
+How an object is detected depends on the light _thresholds_ set for the sensor. A threshold is a number for relative distance of the a return of reflected infrared light. The brighter the light, the nearer the object is. The value for what _near_ means is determined by this threshold. A certain minimum amount of light returned is also set to determine that an object is detected. The two thresholds you can set are:
+
+* **near**: a distance to set to detect objects coming close
+* **detected**: the brightness of infrared light to needed to detect presence of another infrared transmitter.
+
+## Parameters
+
+* **event**: the object detection action to wait for. The detection types (events) are:
+> * ``detected``: some other object is sending out infrared light
+> * ``near``: the sensor detected something within the distance of the near threshold
+
+## Example
+
+Wait for another object sending out infrared light. Show a message on the screen when it's dectected.
+
+```blocks
+brick.showString("Waiting for another", 1);
+brick.showString("robot to appear...", 2);
+sensors.infraredSensor1.pauseUntil(InfraredSensorEvent.ObjectDetected);
+brick.showString("Hey, I just saw", 1)
+brick.showString("Something!", 2);
+```
+
+## See also
+
+[on event](/reference/sensors/ultrasonic/on-event)

libs/infrared-sensor/docs/reference/sensors/infrared/proximity.md

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+# proximity
+
+Get the promixity of an object measured by the infrared sensor.
+
+```sig
+sensors.infraredSensor1.proximity();
+```
+
+The proximity value returned is a number between `0` and `100` which is a _relative_ measurment of  distance to an object. A value of `0` means something is very close and `100` means something is far away. The proximity is determined by the amount of infrared light reflected back by an object. The proximity value for an object that has a lighter color and smooth surface will be less than an object at the same distance with a darker color and a rough surface.
+
+Proximity isn't an actual measurement units of distance, like in centimeters or meters, but it gives you an idea whether something is close or not so close.
+
+## Returns
+
+* a [number](/types/number) that is `0` for (very near) to `100` (far). The value is relative to the range of the infrared sensor.
+
+## Example
+
+When the infrared sensor on port 4 detects a near object, display its proximity value on the screen.
+
+```blocks
+sensors.infraredSensor4.onEvent(InfraredSensorEvent.ObjectNear, function () {
+    brick.clearScreen()
+    brick.showValue("proximity", sensors.infraredSensor4.proximity(), 1)
+})
+```
+
+## See also
+
+[on event](/reference/sensors/infrared/on-event), [pause until](/reference/sensors/infrared/pause-until)