Revert "deprecate embedded browser (#12163)"

This reverts commit 736d8cbac4.

Bring contrib files for older contributions

browser/app/less/inc/buttons.less

@@ -0,0 +1,57 @@
+.btn {
+    border: 0;
+    padding: 5px 10px;
+    font-size: 12px;
+    line-height: 1.5;
+    border-radius: 2px;
+    text-align: center;
+    .transition(all);
+    .transition-duration(300ms);
+
+    &:hover,
+    &:focus {
+        .opacity(0.9);
+    }
+}
+
+/*-----------------------------------
+    Button Variants
+------------------------------------*/
+.btn-variant(@bg-color, @color) {
+    color: @color;
+    background-color: @bg-color;
+
+    &:hover,
+    &:focus {
+        color: @color;
+        background-color: darken(@bg-color, 6%);
+    }
+
+
+}
+
+.btn-block {
+    display: block;
+    width: 100%;
+}
+
+.btn-white {
+    .btn-variant(#fff, darken(@text-color, 20%));
+}
+
+.btn-link {
+    .btn-variant(#eee, #545454);
+}
+
+.btn-danger {
+    .btn-variant(@red, @white);
+}
+
+.btn-primary {
+    .btn-variant(@blue, @white);
+}
+
+.btn-success {
+    .btn-variant(@green, @white);
+}
+//-----------------------------------