Add supporting themes required for Lotusdocs

themes/twbs/bootstrap/scss/forms/_validation.scss

@@ -0,0 +1,12 @@
+// Form validation
+//
+// Provide feedback to users when form field values are valid or invalid. Works
+// primarily for client-side validation via scoped `:invalid` and `:valid`
+// pseudo-classes but also includes `.is-invalid` and `.is-valid` classes for
+// server-side validation.
+
+// scss-docs-start form-validation-states-loop
+@each $state, $data in $form-validation-states {
+  @include form-validation-state($state, $data...);
+}
+// scss-docs-end form-validation-states-loop