simplepaint, update manual with keyboard controls

src/activities/simplepaint/ActivityInfo.qml

@@ -32,7 +32,11 @@ ActivityInfo {
   //: Help prerequisite
   prerequisite: ""
   //: Help manual
-  manual: qsTr("Select a color and paint the rectangles as you like to create a drawing.")
+  manual: qsTr("Select a color and paint the rectangles as you like to create a drawing.") + ("<br><br>") +
+          qsTr("<b>Keyboard controls:</b>") + ("<br>") +
+          qsTr("-Use Arrow keys to navigate") + ("<br>") +
+          qsTr("-Use Space or Enter key to paint") + ("<br>") +
+          qsTr("-Use Tab key to switch between the color selector and the painting area")
   credit: ""
   section: "fun"
   createdInVersion: 4000