add squeekboard toggle button

config/Config.qml

@@ -47,6 +47,16 @@ Singleton {
         return needsExecFlag.includes(env.split("/").pop()) ? [env, "-e"] : [env];
     }
 
+    // ---- On-screen keyboard ----------------------------------------------
+
+    // Set false to drop the keyboard button. It also hides itself where the
+    // unit below is not installed.
+    readonly property bool showOsk: true
+
+    // The user unit squeekboard runs as. Showing the keyboard starts it if it
+    // is not already up; hiding it leaves the unit running.
+    readonly property string oskUnit: "squeekboard.service"
+
     // ---- Wifi ------------------------------------------------------------
 
     // Set false to drop the wifi button. It also hides itself where there is no