Updated default button card styles to support multiline buttons (#43)

* Updated default button card styles to support multiline buttons

Ref DES-160

* Center-aligned button text

Author: sanne-san

assets/built/screen.css

@@ -2374,7 +2374,11 @@ blockquote.kg-blockquote-alt {
 /* Button */
 
 .kg-card.kg-button-card .kg-btn {
+    height: unset;
+    padding: .6em 1.2em;
+    text-align: center;
     font-size: 1em;
+    line-height: 1.2em;
 }
 
 /* Header */