add default button styles

src/scss/_base.scss

@@ -58,3 +58,9 @@ a,
 button {
 	@include font-link();
 }
+
+button {
+	border-radius: $btn-border-radius;
+	border-width: $btn-border-width;
+	border-color: $btn-border-color;
+}

src/scss/_variables.scss

@@ -14,6 +14,10 @@ $bp-max-xl: 1199.98px;
 
 $column-max-width: 1140px;
 
+$btn-border-radius: 12px;
+$btn-border-width: 0;
+$btn-border-color: currentColor;
+
 $color-body: $color__neutral-700;
 $background-color: $color__white;
 

src/scss/style.scss

@@ -27,3 +27,11 @@
 .h6 {
 	@extend h6;
 }
+
+.button {
+	@extend button;
+}
+
+.a {
+	@extend a;
+}