Added a 'debug' option that shows or hides debug traces to console

On certain string occurances the plugin would send traces to the console log. I added an optional 'debug' parameter which controls, if those console traces are displayed or not and set it to false by default.

Besides not wanting to show a plugin's own development/debug traces in projects I used the plugin in, I noticed that the plugin would happily fill the console with traces. If a tab was open that ran a page with the typer plugin and you'd return to that tab after browsing in another tab, there sometimes would come a slight delay/unresponsiveness caused by the console being filled with hundreds and thousands of traces.

Additionally, I made the file references in test.html relative.