feat(docs-infra): add the ability to expose globals (#34237)

Adds the ability to expose global symbols in the API docs via the `@globalApi` tag. Also supports optionally setting a namespace which will be added to the name automatically (e.g. `foo` will be renamed to `ng.foo`). Relevant APIs should also be exported through the `global.ts` file which will show up under `core/global`.

PR Close #34237

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

@@ -0,0 +1,26 @@
+/**
+ * @dgProcessor updateGlobalApiPath
+ *
+ * If a global API has a namespace, its name will contain a dot which will cause its
+ * URL to look like a file path. This processor updates it so it's less ambiguous.
+ */
+module.exports = function updateGlobalApiPathProcessor() {
+  return {
+    $runAfter: ['computePathsProcessor'],
+    $runBefore: ['processNgModuleDocs'],
+    $process: function(docs) {
+      docs.forEach(doc => {
+        if (doc.global && doc.globalNamespace) {
+          // We need to change the path to camel case, because having a dot
+          // in the URL will make it look like a file path.
+          const name = doc.unprefixedName;
+          const fileName = doc.globalNamespace + name[0].toUpperCase() + name.slice(1);
+
+          doc.path = `${doc.moduleDoc.moduleFolder}/${fileName}`;
+          doc.outputPath =
+              `${doc.moduleDoc.moduleFolder}/${fileName}.json`;
+        }
+      });
+    }
+  };
+};