Start on the 'brick' api topics (#280)

* Start on the 'brick' api topics

* Add the delay to clear screen example

* Better output for clearsceen example

docs/reference/brick/clear-screen.md

@@ -0,0 +1,22 @@
+# clear Screen
+
+Clear any text or numbers displayed on the screen. The screen will be blank.
+
+```sig
+brick.clearScreen();
+```
+
+## Example
+
+Clear the screen after displaying the message.
+
+```blocks
+brick.showString("This message will", 1);
+brick.showString("self-destruct in:", 2);
+brick.showString("seconds", 5);
+for (let i = 0; i < 10; i++) {
+    brick.showNumber(10 - i, 4);
+    loops.pause(1000);
+}
+brick.clearScreen();
+```