add example image to packages and CI

example/default.nix

@@ -0,0 +1,37 @@
+{ pkgs, lib, ... }: {
+  time.timeZone = "America/New_York";
+  users.users.root.initialPassword = "root";
+  networking = {
+    hostName = "example";
+    useDHCP = false;
+    interfaces = {
+      wlan0.useDHCP = true;
+      eth0.useDHCP = true;
+    };
+  };
+  raspberry-pi-nix.board = "bcm2711";
+  hardware = {
+    raspberry-pi = {
+      config = {
+        all = {
+          base-dt-params = {
+            BOOT_UART = {
+              value = 1;
+              enable = true;
+            };
+            uart_2ndstage = {
+              value = 1;
+              enable = true;
+            };
+          };
+          dt-overlays = {
+            disable-bt = {
+              enable = true;
+              params = { };
+            };
+          };
+        };
+      };
+    };
+  };
+}