Correct the command to build javascript from typescript (#359)

The command given in the document does not exist and shows help instead. The issue is with the case of the command. It has to be buildJavascript and not buildJavaScript.

Author: dmitryd

Documentation/Testing/CoreTesting.rst

@@ -255,7 +255,7 @@ Luckily, `runTests.sh` also helps us to build JavaScript and CSS assets:
 
 ..  code-block:: shell
 
-    Build/Scripts/runTests.sh -s buildJavaScript
+    Build/Scripts/runTests.sh -s buildJavascript
     Build/Scripts/runTests.sh -s buildCss
 
 Again, this utilizes all the needed containers for the proper NodeJS environment, so you have