docs(upgrade): add guide about downgradeModule() (#18487) (#18487)

PR Close #18487

PR Close #18487

aio/content/guide/upgrade.md

@@ -1,7 +1,7 @@
 # Upgrading from AngularJS to Angular
 
-_Angular_ is the name for the Angular of today and tomorrow.
-_AngularJS_ is the name for all v1.x versions of Angular.
+_Angular_ is the name for the Angular of today and tomorrow.<br />
+_AngularJS_ is the name for all 1.x versions of Angular.
 
 AngularJS apps are great.
 Always consider the business case before moving to Angular.
@@ -195,7 +195,7 @@ transition period.
 
 ### How ngUpgrade Works
 
-The primary tool provided by ngUpgrade is called the `UpgradeModule`.
+One of the primary tools provided by ngUpgrade is called the `UpgradeModule`.
 This is a module that contains utilities for bootstrapping and managing hybrid
 applications that support both Angular and AngularJS code.
 
@@ -252,7 +252,7 @@ frameworks in how it actually works.
 </table>
 
 Even accounting for these differences you can still have dependency injection
-interoperability. The `UpgradeModule` resolves the differences and makes
+interoperability. `upgrade/static` resolves the differences and makes
 everything work seamlessly:
 
 * You can make AngularJS services available for injection to Angular code
@@ -569,7 +569,7 @@ So, you can write an Angular component and then use it from AngularJS
 code. This is useful when you start to migrate from lower-level
 components and work your way up. But in some cases it is more convenient
 to do things in the opposite order: To start with higher-level components
-and work your way down. This too can be done using the `UpgradeModule`.
+and work your way down. This too can be done using the `upgrade/static`.
 You can *upgrade* AngularJS component directives and then use them from
 Angular.
 
@@ -710,7 +710,7 @@ and then provide the input and output using Angular template syntax:
 When you are using a downgraded Angular component from an AngularJS
 template, the need may arise to *transclude* some content into it. This
 is also possible. While there is no such thing as transclusion in Angular,
-there is a very similar concept called *content projection*. The `UpgradeModule`
+there is a very similar concept called *content projection*. `upgrade/static`
 is able to make these two features interoperate.
 
 Angular components that support content projection make use of an `<ng-content>`

aio/content/navigation.json

@@ -514,6 +514,11 @@
               "title": "Upgrading Instructions",
               "tooltip": "Incrementally upgrade an AngularJS application to Angular."
             },
+            {
+              "url": "guide/upgrade-lite",
+              "title": "Lazy-loading Angular into AngularJS",
+              "tooltip": "Upgrade from AngularJS to Angular in a more flexible way."
+            },
             {
               "url": "guide/ajs-quick-reference",
               "title": "AngularJS-Angular Concepts",

packages/upgrade/src/static/downgrade_module.ts

@@ -18,8 +18,6 @@ import {NgAdapterInjector} from './util';
 
 
 /**
- * <!-- TODO(gkalpak): Add link to guide. -->
- *
  * @description
  *
  * A helper function for creating an AngularJS module that can bootstrap an Angular module
@@ -49,6 +47,9 @@ import {NgAdapterInjector} from './util';
  *
  * {@example upgrade/static/ts/lite/module.ts region="basic-how-to"}
  *
+ * For more details on how to use `downgradeModule()` see
+ * [Upgrading for Performance](guide/upgrade-lite).
+ *
  * @usageNotes
  *
  * Apart from `UpgradeModule`, you can use the rest of the `upgrade/static` helpers as usual to
@@ -84,6 +85,9 @@ import {NgAdapterInjector} from './util';
  * especially in change-detection-heavy applications, but leaves it up to the developer to manually
  * notify each framework as needed.
  *
+ * For a more detailed discussion of the differences and their implications, see
+ * [Upgrading for Performance](guide/upgrade-lite).
+ *
  * <div class="alert is-helpful">
  *
  *   You can manually trigger a change detection run in AngularJS using