Add Zadig note to the readme

This is cleaner than directing to a document name that must then be searched for the word Zadig

Author: will-v-pi

README.md

@@ -1658,3 +1658,8 @@ this requirement (see the [hello_usb](https://github.com/raspberrypi/pico-exampl
 If you ctrl+c out of the middle of a long operation, then libusb seems to get a bit confused, which means we aren't able
 to unlock our lockout of USB MSD writes (we have turned them off so the user doesn't step on their own toes). Simply running
 `picotool info` again will unlock it properly the next time (or you can reboot the device).
+
+### Zadig
+To communicate with RP2040 in BOOTSEL mode on Windows, you will need to install a driver. To do this, download and run [Zadig](http://zadig.akeo.ie), select `RP2 Boot (Interface 1)` from the dropdown box and select `WinUSB` as the driver, and click on the "Install Driver" button. Wait for the installation to complete - this may take a few minutes.
+
+This is only required for RP2040.

main.cpp

@@ -8731,7 +8731,7 @@ int main(int argc, char **argv) {
                             if (tries) {
 #if defined(_WIN32)
                                 if (settings.force_rp2040) {
-                                    fos << " You may need to install a driver via Zadig. See \"Getting started with Raspberry Pi Pico\" for more information.";
+                                    fos << " You may need to install a driver via Zadig. See Zadig in the README (https://github.com/raspberrypi/picotool#zadig) for more information.";
                                 }
 #endif
                                 fos << " It is possible the device is not responding, and will have to be manually entered into BOOTSEL mode.\n";
@@ -8756,7 +8756,7 @@ int main(int argc, char **argv) {
                                     " appears to have a USB serial connection, but picotool was unable to connect. Maybe try 'sudo' or check your permissions.");
     #else
                             printer(dr_vidpid_bootrom_cant_connect,
-                                    " appears to be in BOOTSEL mode, but picotool was unable to connect. You may need to install a driver via Zadig. See \"Getting started with Raspberry Pi Pico\" for more information");
+                                    " appears to be in BOOTSEL mode, but picotool was unable to connect. You may need to install a driver via Zadig. See Zadig in the README (https://github.com/raspberrypi/picotool#zadig) for more information");
                             printer(dr_vidpid_stdio_usb_cant_connect,
                                     " appears to have a USB serial connection, but picotool was unable to connect.");
     #endif