feat(@angular/cli): implement --registry for ng add (#14285)

Closes 14189

Author: tiaguinho

packages/angular/cli/commands/add-impl.ts

@@ -64,7 +64,7 @@ export class AddCommand extends SchematicCommand<AddCommandSchema> {
         packageMetadata = await fetchPackageMetadata(
           packageIdentifier.name,
           this.logger,
-          { usingYarn },
+          { registry: options.registry, usingYarn },
         );
       } catch (e) {
         this.logger.error('Unable to fetch package metadata: ' + e.message);
@@ -114,7 +114,7 @@ export class AddCommand extends SchematicCommand<AddCommandSchema> {
         const manifest = await fetchPackageManifest(
           packageIdentifier,
           this.logger,
-          { usingYarn },
+          { registry: options.registry, usingYarn },
         );
 
         collectionName = manifest.name;

packages/angular/cli/commands/add.json

@@ -18,6 +18,18 @@
             "$source": "argv",
             "index": 0
           }
+        },
+        "registry": {
+          "description": "The NPM registry to use.",
+          "type": "string",
+          "oneOf": [
+            {
+              "format": "uri"
+            },
+            {
+              "format": "hostname"
+            }
+          ]
         }
       },
       "required": [