Day 2: made this navigation menu consistent across days

Created this boilerplate code that I can then include in each day's project, on top
so at least there's _some_ sort of consistency :)

but since I haven't done much else, I thought of displaying your computer's IP Address:
172.69.214.161

Here's what else a website might find out from your browser:
- the User Agent string. Basically - what browser you're using:
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; [email protected])