Made docs sidebar a slight bit easier to scroll

Now it easily goes off the page, made it indapentally scrollable.
Will probably do something different in future as it grows more.

resources/sass/_blocks.scss

@@ -274,4 +274,6 @@
 .sticky-sidebar {
   position: sticky;
   top: $-m;
+  max-height: calc(100vh - #{$-m});
+  overflow-y: auto;
 }