Update Readme, formatting, and testing setup

[bakerkretzmar]

• Updates the Readme to improve and simplify the code examples and emphasize the @routes Blade directive over the NPM package and JS plugins.
• Replaces Jest (and a few other dependencies) with Vitest, which is faster and makes testing our types easier.
• Adds actual tests for the types and a command to run them.
• Uses standard Jest/Chai assertion syntax in all tests, instead of the custom assert stuff, for ease of contribution and maintenance.
• Installs prettier and run it to format Ziggy's JS code.