Recently I've updated these with a new "Upside-down" view to complement the rear view, giving a pinout in the right orientation to match your project.
The Pico sites are all hand-coded single HTML pages with supporting CSS and minimal JS. They are set up to optionally install as a "Desktop" web app. They also degrade into a somewhat usable table in lieu of CSS and use vector graphics (for the board itself) to be viewable and printable at any size.
Finally, hidden behind "Advanced" is a pinout of the test pads and special function pins!
[1] - https://web.archive.org/web/20130505194305/pi.gadgetoid.com/... [2] - https://pico.pinout.xyz [3] - https://pico2.pinout.xyz
Bonus points if it could generate example initialisation code for the selected pins on the fly or maybe even an example snippet of code to get the peripheral going.
And code gen is something I'm looking at with the RP2350A pinout [2] where the JSON export would allow someone to plug it into any tool they like. (KiCAD symbol gen, C/MicroPython init code, etc)
It's difficult to strike a balance between features/minimalism but I'm increasingly drawn to the idea of a full (STM32Cube-like if you're familiar with it) configurator for Pico/RP2 based boards.