Add new Cockpit login needle using the text box area

The background seems to be different in different tests, even
the reduced area I tried most recently seems to be different in
some runs. So let's just match in the text area instead. This
captures some "Fedora" text so it should still notice if branding
is broken.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/cockpit/login-textbox.json

@@ -0,0 +1,15 @@
+{
+  "area": [
+    {
+      "width": 81,
+      "type": "match",
+      "xpos": 108,
+      "height": 68,
+      "ypos": 233
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "cockpit_login"
+  ]
+}