Resolve #3457688 "Sub module version"

Closes #3457688

modules/environment_indicator_navigation/css/style.css

+/* Active environment button background and font colors. */
+.admin-toolbar .toolbar-button.toolbar-button--environment-indicator,
+.admin-toolbar .toolbar-button.toolbar-button--environment-indicator-label {
+  color: var(--env-indicator-fg-color);
+  background-color: var(--env-indicator-bg-color);
+}
+
+/* Collapsed button label display */
+html:not([data-admin-toolbar="expanded"]) .toolbar-button--environment-indicator {
+  padding-inline: var(--admin-toolbar-space-8);
+  height: var(--admin-toolbar-space-40);
+}
+html:not([data-admin-toolbar="expanded"]) .toolbar-button--collapsible.toolbar-button--environment-indicator .toolbar-button__label {
+  clip: unset;
+  clip-path: unset;
+  position: relative;
+  height: var(--admin-toolbar-space-40);
+  width: calc(40px - (2 * var(--admin-toolbar-space-8)));
+  opacity: 1;
+  line-height: var(--admin-toolbar-space-40);
+  font-variation-settings: "wght" 500;
+}
+
+/* Add fade effect to collapsed button label */
+html:not([data-admin-toolbar="expanded"]) .toolbar-button--environment-indicator .toolbar-button__label {
+  --mask: linear-gradient(to right,rgba(0, 0, 0, 1) 0, rgba(0, 0, 0, 1) 60%,rgba(0, 0, 0, 0) 99%, rgba(0, 0, 0, 0) 0) 100% 50% / 100% 100% repeat-x;
+  -webkit-mask: var(--mask);
+  mask: var(--mask);
+}
+
+/* Left environment indicator */
+.admin-toolbar {
+  margin-left: var(--admin-toolbar-space-8);
+}
+
+.admin-toolbar::before {
+  height: 100%;
+  width: var(--admin-toolbar-space-12);
+  content: '';
+  position: absolute;
+  display: block;
+  top: 0;
+  left: calc(-1 * var(--admin-toolbar-space-8));
+  background-color: var(--env-indicator-bg-color);
+}