fix(demo): fix spacing in flex layout for aura/base themes

Close #177

Author: paodb

src/test/java/com/flowingcode/vaadin/addons/googlemaps/AddMarkersDemo.java

@@ -143,9 +143,7 @@ protected void createGoogleMapsDemo(String apiKey) {
 
     FlexLayout layout = new FlexLayout();
     layout.setFlexWrap(FlexWrap.WRAP); // hide-source
-    addMarker.addClassName("margin-button"); // hide-source
-    colorCB.addClassName("margin-button"); // hide-source
-    labelText.addClassName("margin-button"); // hide-source
+    layout.getStyle().set("gap", "var(--lumo-space-s, var(--vaadin-gap-m))"); // hide-source
     layout.add(colorCB, draggable, withRightClick, withLabel, labelText, addMarker);
     layout.setAlignItems(Alignment.BASELINE); // hide-source
     layout.getStyle().set("margin-top", "0"); // hide-source

src/test/java/com/flowingcode/vaadin/addons/googlemaps/DisableUIControlsDemo.java

@@ -43,6 +43,7 @@ protected void createGoogleMapsDemo(String apiKey) {
 
     FlexLayout layout = new FlexLayout();
     layout.setFlexWrap(FlexWrap.WRAP);
+    layout.getStyle().set("gap", "var(--lumo-space-s, var(--vaadin-gap-m))"); // hide-source
 
     Checkbox disableMapTypeControl =
         new Checkbox("Disable map type control", e -> gmaps.disableMapTypeControl(e.getValue()));