jatkinson1000/add copy code button option

[jatkinson1000]

This builds on the seemingly stagnated PR #27 of @pbklink to remove the redundant else clause and comments as requested.

To quote @pbklink:

Includes a feature where a copy button can be added to all code blocks in a website.
This feature can be enabled by setting the following parameter in config.toml
copyCodeButtonEnabled = true
Note that this feature requires a JavaScript script. This script is included under the new static/js directory.