Implemented phase 6 for the POC prototype in the Website service.

Services/Website/Sources/Library/Internal/Components/PasskeyUnsupported.swift

@@ -0,0 +1,22 @@
+import Elementary
+
+/// What a browser without passkeys is told. Shown by default; `js/passkey.js` hides it once it finds WebAuthn.
+struct PasskeyUnsupported: HTML {
+
+    // MARK: Computed
+
+    var body: some HTML {
+        div(
+            .class("notice"),
+            .custom(name: "data-passkey-unsupported", value: "")
+        ) {
+            p {
+                strong {
+                    "This browser can't use passkeys."
+                }
+                " Open this page in Safari, Chrome, Edge or Firefox on a device with a screen lock — with scripts allowed."
+            }
+        }
+    }
+
+}