Run script example

This example demonstrates calling emscripten:run_script/1 and emscripten:run_script/2 to run Javascript from Erlang.

It runs four Javascript scripts:

• One script from the main thread, synchronously, that prints a line to the console and displays an alert
• One script from the main thread, asynchronously, that prints a line to the console and displays an alert
• One script from the worker thread that prints a line to the console
• One script that updates the DOM to display the time required for first script to run

On non-SMP builds, it demonstrates the fact that Erlang continues to run when emscripten:run_script/2 is called with [main_thread] as a counter is incremented while waiting for first line to be printed. The value is unset

Beyond the counter, this example also demonstrates manipulating DOM (in the main thread) using JS function.