Fix Nextra margin-top in nested lists (#2686)

Before:

<img width="846" alt="image"
src="https://github.com/WATonomous/infra-config/assets/5977478/965bf0bb-d26b-40fa-a9ac-4a959b78b4f8">


After:

<img width="845" alt="image"
src="https://github.com/WATonomous/infra-config/assets/5977478/d7dcc120-e891-4a2a-aa6d-28a70a705717">


The problem is that by default, Nextra applies `first:nx-mt-0` on
`:first-child`. But in some cases (as shown above), the nested list is
not the first child. In the example above, the first child is the `a`
tag:

<img width="1413" alt="image"
src="https://github.com/WATonomous/infra-config/assets/5977478/e3e326b2-f8c1-47bb-8678-808b61262b03">

The fix is to use `:first-of-type` instead.

Related: shuding/nextra#863

styles/global.css

@@ -123,3 +123,10 @@ select:focus,
 textarea {
   font-size: 16px;
 }
+
+
+/* Fix margin issue for nested lists: https://github.com/shuding/nextra/issues/863#issuecomment-2068517369 */
+li > ul.first\:nx-mt-0:first-of-type,
+li > ol.first\:nx-mt-0:first-of-type {
+  margin-top: 0;
+}