feat: Import a separate file for ICE servers

[tomershvueli]

This PR slightly speaks towards issue #30. By extrapolating the ICE servers array definition to a separate file, an automated build process can override these values easier by simply overwriting this file, instead of having to edit the original script.js file.

Since the new JS file is being imported above the script.js in the index.html page, all current Docker builds, etc should continue to work fine without a hitch.