Make frontend easier to develop

[LouisBrunner]

Most static files are not adapted for development (prepended by /findwork/, the API URL is hardcoded...) or could benefit from Quality of Life changes.

List of changes:

• Ignore compiled JS
• Make package private (prevent publishing to NPM by mistake)
• Add NPM scripts to ease compilation
• Make API_URL variable so it can be switched for the development server
• Add a debug route to handle the production routes in index.html, work.css… (prepended with /findwork/)

[nrc]

These all look like good changes, thank you!