chore: fix bazel failure (#11487)

Restores a file that was removed in #11481 and ended up breaking the Bazel build.

src/cdk-experimental/scrolling/tsconfig-build.json

@@ -2,7 +2,7 @@
   "extends": "../tsconfig-build",
   "files": [
     "public-api.ts",
-    "../typings.d.ts"
+    "./typings.d.ts"
   ],
   "angularCompilerOptions": {
     "annotateForClosureCompiler": true,

src/cdk-experimental/scrolling/typings.d.ts

@@ -0,0 +1 @@
+declare var module: {id: string};