lockscreen: replace lockscreen example

The new one uses the pam module and looks much nicer.

lockscreen/LockContext.qml

@@ -0,0 +1,54 @@
+import QtQuick
+import Quickshell
+import Quickshell.Services.Pam
+
+Scope {
+	id: root
+	signal unlocked()
+	signal failed()
+
+	// These properties are in the context and not individual lock surfaces
+	// so all surfaces can share the same state.
+	property string currentText: ""
+	property bool unlockInProgress: false
+	property bool showFailure: false
+
+	// 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();
+			} else {
+				root.currentText = "";
+				root.showFailure = true;
+			}
+
+			root.unlockInProgress = false;
+		}
+	}
+}