Migrate docs from the other repo

docs/reference/led/fade-in.md

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+# Fade in
+
+Gradually increase the [LED screen](/microbit/device/screen) brightness until the LED lights are at full brightness.
+
+```sig
+led.fadeIn(700);
+```
+
+### Parameters
+
+* ms - [Number](/microbit/reference/types/number); the speed by which the screen brightness is increased, expressed in milliseconds (1,000 milliseconds = 1 second). The smaller the number the faster the screen brightness increased.
+
+### Example: fading dot
+
+The following code turns on centre LED and then gradually increases and decreases the screen brightness (the centre LED pulses 5 times):
+
+```blocks
+led.plot(2, 2)
+for (let i = 0; i < 5; i++) {
+    led.setBrightness(0)
+    led.fadeIn(100)
+    basic.pause(100)
+    led.fadeOut(100)
+}
+```
+
+### Lessons
+
+[glowing sword](/microbit/lessons/glowing-sword)
+
+### See also
+
+[brightness](/microbit/reference/led/brightness), [fade out](/microbit/reference/led/fade-out), [set brightness](/microbit/reference/led/set-brightness)
+