Finish the README and add the wiki in English, Danish and Bahasa Malaysia

Doxygen builds the source documentation without warnings.

Task: MIL-007#1
Task: MIL-007#2
Task: MIL-007#3

wiki/Play.md

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+# Play
+
+🌐 **English** · [Dansk](Play-da) · [Bahasa Malaysia](Play-ms)
+
+## Controls
+
+| Key | Action |
+| --- | --- |
+| Up arrow | Move the turtle one step north. The turtle cannot move back, left or right. |
+
+## Rules
+
+1. Cars appear on the right edge in random lanes and drive left. The top and
+   bottom 50 pixels are a safe zone with no cars.
+2. Reach the top edge to cross. The turtle returns to the start, the level goes
+   up by one and the cars become faster.
+3. Touching a car ends the game. `GAME OVER` is shown in the centre; click the
+   window to close it.
+
+## Tips
+
+- Wait for a gap: a new car is created on about one frame in six.
+- Every level adds the same speed step, so later levels need quick, short moves.
+
+Back to [Home](Home).