feat: add onClickLogin on the main GUI component

Allows overriding what happens when the Login button in the header
is clicked. In some cases we want to be able to open a popup, not
just render a user/pass dialog as in current Scratch.

Author: georgyangelov

packages/scratch-gui/src/components/gui/gui.jsx

@@ -99,6 +99,7 @@ const GUIComponent = props => {
         onClickAccountNav,
         onCloseAccountNav,
         onLogOut,
+        onClickLogin,
         onOpenRegistration,
         onToggleLoginOpen,
         onActivateCostumesTab,
@@ -274,6 +275,7 @@ const GUIComponent = props => {
                     onClickLogo={onClickLogo}
                     onCloseAccountNav={onCloseAccountNav}
                     onLogOut={onLogOut}
+                    onClickLogin={onClickLogin}
                     onOpenRegistration={onOpenRegistration}
                     onProjectTelemetryEvent={onProjectTelemetryEvent}
                     onSeeCommunity={onSeeCommunity}
@@ -463,6 +465,7 @@ GUIComponent.propTypes = {
     onLogOut: PropTypes.func,
     onNewSpriteClick: PropTypes.func,
     onNewLibraryCostumeClick: PropTypes.func,
+    onClickLogin: PropTypes.func,
     onOpenRegistration: PropTypes.func,
     onRequestCloseBackdropLibrary: PropTypes.func,
     onRequestCloseCostumeLibrary: PropTypes.func,