put shell in subdir, and add nix package

shell/lockscreen/LockContext.qml

@@ -0,0 +1,53 @@
+import QtQuick
+import Quickshell
+import Quickshell.Services.Pam
+
+Scope {
+    id: root
+
+    property string currentText: ""
+    property bool unlockInProgress: false
+    property bool showFailure: false
+    signal unlocked
+    signal failed
+
+    // Clear the failure text once the user starts typing.
+    onCurrentTextChanged: showFailure = false
+
+    function tryUnlock() {
+        if (currentText === "")
+            return;
+
+        root.unlockInProgress = true;
+        pam.start();
+    }
+
+    PamContext {
+        id: pam
+
+        // Its best to have a custom pam config for quickshell, as the system one
+        // might not be what your interface expects, and break in some way.
+        // This particular example only supports passwords.
+        configDirectory: "pam"
+        config: "password.conf"
+
+        // pam_unix will ask for a response for the password prompt
+        onPamMessage: {
+            if (this.responseRequired) {
+                this.respond(root.currentText);
+            }
+        }
+
+        // pam_unix won't send any important messages so all we need is the completion status.
+        onCompleted: result => {
+            if (result == PamResult.Success) {
+                root.unlocked();
+                root.currentText = "";
+            } else {
+                root.showFailure = true;
+            }
+
+            root.unlockInProgress = false;
+        }
+    }
+}