build(docs-infra): separate NgModules from Classes in API docs (#25734)

PR Close #25734

aio/tools/transforms/angular-api-package/processors/processNgModuleDocs.js

@@ -0,0 +1,18 @@
+module.exports = function processNgModuleDocs() {
+  return {
+    $runAfter: ['extractDecoratedClassesProcessor'],
+    $runBefore: ['docs-processed'],
+    $process(docs) {
+      docs.forEach(doc => {
+        if (doc.docType === 'ngmodule') {
+          Object.keys(doc.ngmoduleOptions).forEach(key => {
+            const value = doc.ngmoduleOptions[key];
+            if (value && !Array.isArray(value)) {
+              doc.ngmoduleOptions[key] = [value];
+            }
+          });
+        }
+      });
+    }
+  };
+};