Revert "Use jekyll-assets"

This reverts commit 9062937951.

_sass/modules/_buttons.scss

@@ -0,0 +1,34 @@
+.btn {
+  color: $color-white;
+  display: flex;
+  background: $color-blue-5;
+  align-items: center;
+  padding: $spacing-unit/4 $spacing-unit/2;
+  border-radius: 8px;
+  text-decoration: none;
+
+  &:hover {
+    background: $color-blue-4;
+    cursor: pointer;
+    text-decoration: none;
+  }
+}
+
+.btn:visited {
+  color: $color-white;
+}
+
+.btn-row {
+  display: flex;
+  justify-content: center;
+  margin-bottom: 0;
+
+  .btn:not(:first-child) {
+    margin-left: $spacing-unit / 2;
+  }
+}
+
+.icon {
+  vertical-align: middle;
+  margin-right: $spacing-unit / 4;
+}