Loading local modules on Pico

For starters, have a look at: http://www.espruino.com/File+IO

From the espruino docs:

On the original Espruino board there's a Micro SD card slot built-in,
or on the Espruino Pico you'll have to wire a card up externally and
then tell Espruino about it with E.connectSDCard:

Once you have wired a SD card to the appropriate pins on your Pico, tell the Pico about it, like so:

// Wire up up MOSI, MISO, SCK and CS pins (along with 3.3v and GND)
SPI1.setup({mosi:B5, miso:B4, sck:B3});
E.connectSDCard(SPI1, B6 /*CS*/);
// see what's on the device
console.log(require("fs").readdirSync());