Fix border radius on mixed type buttons (saadeghi#1159)

* Fix border radius on mixed type buttons

Currently, if you have buttons of different types (`a` vs `button` for example), the button styling breaks because the selectors depend on the button type:

Change to using child selectors as this doesn't care what type of child exists.

* bring back `:not` selectors for button

because otherwise, border radius of first and last children will be wrong

Co-authored-by: Pouya Saadeghi <pouya.saadeghi@gmail.com>

src/utilities/styled/button.css

@@ -1,35 +1,35 @@
 /* group */
 .btn-group,
 .btn-group.btn-group-horizontal {
-  .btn:not(:first-of-type):not(:last-of-type) {
+  .btn:not(:first-child):not(:last-child) {
     border-top-left-radius: 0;
     border-top-right-radius: 0;
     border-bottom-left-radius: 0;
     border-bottom-right-radius: 0;
   }
-  .btn:first-of-type:not(:last-of-type) {
+  .btn:first-child:not(:last-child) {
     @apply -ml-px -mt-0;
     border-top-left-radius: var(--rounded-btn, 0.5rem);
     border-top-right-radius: 0;
     border-bottom-left-radius: var(--rounded-btn, 0.5rem);
     border-bottom-right-radius: 0;
   }
-  .btn:last-of-type:not(:first-of-type) {
+  .btn:last-child:not(:first-child) {
     border-top-left-radius: 0;
     border-top-right-radius: var(--rounded-btn, 0.5rem);
     border-bottom-left-radius: 0;
     border-bottom-right-radius: var(--rounded-btn, 0.5rem);
   }
 }
 .btn-group.btn-group-vertical {
-  .btn:first-of-type:not(:last-of-type) {
+  .btn:first-child:not(:last-child) {
     @apply -ml-0 -mt-px;
     border-top-left-radius: var(--rounded-btn, 0.5rem);
     border-top-right-radius: var(--rounded-btn, 0.5rem);
     border-bottom-left-radius: 0;
     border-bottom-right-radius: 0;
   }
-  .btn:last-of-type:not(:first-of-type) {
+  .btn:last-child:not(:first-child) {
     border-top-left-radius: 0;
     border-top-right-radius: 0;
     border-bottom-left-radius: var(--rounded-btn, 0.5rem);