css button: add radius and shadow (#455)

diff --git a/netbeans.apache.org/src/content/scss/base/_settings.scss b/netbeans.apache.org/src/content/scss/base/_settings.scss
index 01fa130..541471f 100644
--- a/netbeans.apache.org/src/content/scss/base/_settings.scss
+++ b/netbeans.apache.org/src/content/scss/base/_settings.scss
@@ -306,6 +306,8 @@
 $button-background-hover-lightness: -20%;
 $button-hollow-hover-lightness: -50%;
 $button-transition: background-color 0.25s ease-out, color 0.25s ease-out;
+$button-border-radius: 4px;
+$button-box-shadow: 0px 2px 2px rgba(0, 0, 0, 0.2);
 
 // 12. Button Group
 // ----------------