fix: align buttons in horizontal orientation

Close #174

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/twincolgrid/TwinColGrid.java

@@ -375,6 +375,7 @@ private VerticalLayout createVerticalContainer(boolean reverse) {
 
   private VerticalLayout getVerticalButtonContainer() {
     fakeButtonContainerLabel.getElement().setProperty("innerHTML", " ");
+    fakeButtonContainerLabel.setClassName("fake-button-container-label");
     updateFakeButtonContainerVisiblity();
 
     VerticalLayout vButtonContainer =

src/main/resources/META-INF/resources/frontend/styles/twincol-grid.css

@@ -44,3 +44,7 @@
   color: var(--lumo-error-text-color);
 }
 
+.twincol-grid .fake-button-container-label {
+  font-size: var(--lumo-font-size-s);
+  margin-bottom: calc(var(--vaadin-button-margin, var(--lumo-space-xs))* -1);
+}