Added executeCommand netscript function

doc/source/netscript/singularityfunctions/executeCommand.rst

@@ -0,0 +1,21 @@
+executeCommand() Netscript Function
+========================================
+
+.. js:function:: executeCommand(command)
+
+    :RAM cost: 4 GB
+    :param string commands: The full string of the command.
+
+    If you are not in BitNode-4, then you must have Level 1 of Source-File 4 in order to use this function.
+
+    This function writes the command to the terminal and executes it. This
+    can be used to perform manual hacks. Only one command can be sent at a time.
+
+    Examples:
+
+    .. code-block:: javascript
+
+        await ns.executeCommand('connect CSEC');
+        await ns.executeCommand('hack');
+        await ns.executeCommand('home');
+        // a manual hack will be performed and CSEC will invite you.