Load script from cdn.jsdelivr.net

Resolving the comment #544 (comment)

Author: alexander-yevsyukov

site/layouts/_partials/oss-licenses/licenses.html

@@ -57,5 +57,7 @@
 <!-- The JavaScript Markdown to HTML converter.
 Used in the `assets/js/pages/oss-licenses.js`. -->
 <!--suppress JSUnresolvedLibraryURL -->
-<script src="https://cdn.rawgit.com/showdownjs/showdown/1.9.0/dist/showdown.min.js"
+<script src="https://cdn.jsdelivr.net/npm/showdown@1.9.0/dist/showdown.min.js"
+        integrity="sha384-KpuxVjTC2hfOkg5KV3jSdx1eA6xy0PGS0wNfDrwf4sZBnZdzlIsnkH+LzLkavmH7"
+        crossorigin="anonymous"
         type="text/javascript"></script>