fix: add dependency on @angular/forms

Adds `@angular/forms` to the list of dependencies, because there are around 10 Material components that are importing symbols from it.

Fixes #15085.

Author: crisbeto

src/lib/package.json

@@ -25,7 +25,8 @@
     "@angular/animations": "0.0.0-NG",
     "@angular/cdk": "0.0.0-PLACEHOLDER",
     "@angular/core": "0.0.0-NG",
-    "@angular/common": "0.0.0-NG"
+    "@angular/common": "0.0.0-NG",
+    "@angular/forms": "0.0.0-NG"
   },
   "dependencies": {
     "tslib": "^1.7.1"