Update (.gitignore) to ignore compiled files

Git should ignore all files that are compiled with project repo, and all
images.

(.gitignore) ignore:
* (*.css) compiled with project repo
* (*.js) compiled with project repo
* all images

Exception: Allow git add for modules compiled externally.
Add (script.html) for default layout js sourcing.

Separate the default layout JavaScript sourcing into its own file
(script.html) for modularity. Add (script.html) to default layout
(default.html).