feat: Cornerstone extension viewport default enabledElement handler and installation guides (#2636)

* feat: Add initial doc for mode installation

* fix: cornerstone viewport should have default enabledElement handler

* docs: Add custom mode and extension installation guides

* docs: Add route address for template mode

platform/docs/src/css/custom.css

@@ -207,7 +207,6 @@ article header h3 {
   --ifm-button-background-color: #e8f7f7;
 }
 
-
 .admonition-icon svg {
   fill: #0151d9;
 }
@@ -225,6 +224,19 @@ article header h3 {
   margin-top: 0;
 }
 
+.docusaurus-highlight-code-line {
+  background-color: rgb(206, 208, 211);
+  display: block;
+  margin: 0 calc(-1 * var(--ifm-pre-padding));
+  padding: 0 var(--ifm-pre-padding);
+}
+
+/* If you have a different syntax highlighting theme for dark mode. */
+html[data-theme='dark'] .docusaurus-highlight-code-line {
+  /* Color which works with dark mode syntax highlighting theme */
+  background-color: rgb(100, 100, 100);
+}
+
 /* .DocSearch {
   display: none;
 } */