Add JavaScript and CSS style checker / code formatter

[andresenwc]

Some files are currently formatted using Prettier.

We should set up some framework to ensure that as files are committed, style is upheld in the project.

One option is to enforce this functionality through a pre-commit hook; Prettier provides some documentation on how we could go about adding this.

To close this issue, we would need to:

1. Choose a style checker / code formatter.
2. Reformat all currently existing js and css files.
3. Add some way to maintain code style as we move forward.