Add CLS command doc

Author: boriel

docs/cls.md

@@ -0,0 +1,39 @@
+#CLS
+
+##Syntax
+
+```
+ CLS
+```
+
+##Description
+
+`CLS` is short for *CLear Screen*, and will do just that: it will clear the screen, setting the background
+with the current [PAPER](paper.md) color, and placing the Screen Cursor at (0, 0) - screen top-leftmost corner.
+
+
+##Examples
+
+```
+REM sets the screen black, and INK white
+BORDER 0: PAPER 0: INK 7
+CLS
+PRINT "White text on black background"
+```
+
+
+##Remarks
+
+* This sentence is compatible with Sinclair BASIC 
+
+##See also
+
+* [PRINT](print.md)
+* [AT](at.md)
+* [PAPER](paper.md)
+* [BORDER](border.md)
+* [INVERSE](inverse.md)
+* [INK](ink.md)
+* [ITALIC](italic.md)
+* [BOLD](bold.md)
+* [OVER](over.md)