[pkl-doc] Sort stdlib first on the main page (#165)

pkl-doc/src/main/kotlin/org/pkl/doc/MainPageGenerator.kt

@@ -67,6 +67,14 @@ internal class MainPageGenerator(
   private fun HtmlBlockTag.renderPackages() {
     if (packagesData.isEmpty()) return
 
+    val sortedPackages =
+      packagesData.sortedWith { pkg1, pkg2 ->
+        when {
+          pkg1.ref.pkg == "pkl" -> -1 // always sort the stdlib first
+          else -> pkg1.ref.pkg.compareTo(pkg2.ref.pkg)
+        }
+      }
+
     div {
       classes = setOf("member-group")
 
@@ -79,7 +87,7 @@ internal class MainPageGenerator(
       }
 
       ul {
-        for (pkg in packagesData) {
+        for (pkg in sortedPackages) {
           val packageScope =
             pageScope.packageScopes[pkg.ref.pkg]
             // create scope for previously generated package