Added comment to the docs that saveImageWithTag is deprecated

Summary:
- [x] Explain the **motivation** for making this change.
- [x] Provide a **test plan** demonstrating that the code is solid.
- [x] Match the **code formatting** of the rest of the codebase.
- [x] Target the `master` branch, NOT a "stable" branch.

The CameraRoll docs have a method for `saveImageWithTag`.  I wanted to know how to use it and how it differs from the other methods. So I open the react-native repo and used the source.

I discovered this method is deprecated.  It does use a console warning to notify upon use.  A developer should not have to use a deprecated method to know it's no longer supported.  The docs should state this until it is removed from the library.

```bash
git clone https://github.com/facebook/react-native.git
cd react-native
npm install
cd website
npm install
npm start
open http://localhost:8079/react-native/docs/cameraroll.html
```

Verify there are comments for `saveImageWithTag` method notifying developers that it is deprecated.
Closes #14345

Differential Revision: D5198453

Pulled By: shergin

fbshipit-source-id: 2b74120a1ee450b903cdcff3812a83747dac5bb8

Author: jordanpapaleo

Libraries/CameraRoll/CameraRoll.js

@@ -121,9 +121,12 @@ class CameraRoll {
   static GroupTypesOptions: Object = GROUP_TYPES_OPTIONS;
   static AssetTypeOptions: Object = ASSET_TYPE_OPTIONS;
 
+  /**
+   * `CameraRoll.saveImageWithTag()` is deprecated. Use `CameraRoll.saveToCameraRoll()` instead.
+   */
   static saveImageWithTag(tag: string): Promise<Object> {
     console.warn(
-      'CameraRoll.saveImageWithTag is deprecated. Use CameraRoll.saveToCameraRoll instead',
+      '`CameraRoll.saveImageWithTag()` is deprecated. Use `CameraRoll.saveToCameraRoll()` instead.',
     );
     return this.saveToCameraRoll(tag, 'photo');
   }