Add Material Components iOS as a dependency.

ios/third_party/material_components_ios/README.chromium

Index: ios/third_party/material_components_ios/README.chromium
diff --git a/ios/third_party/material_components_ios/README.chromium b/ios/third_party/material_components_ios/README.chromium
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+Name: Material Components for iOS
+URL: https://github.com/material-components/material-components-ios
+Version: 0
+Revision: 4e5a18715bedf3ada7fd35ba9d2d41082fbf7437
+License: Apache 2.0
+License File: LICENSE
+Security Critical: yes
+
+Description:
+Material Components is a production-quality UI framework focused on design
+details. The framework is designed to be a stable, documented and pixel-perfect
+set of UI components suitable for shipping high-quality material applications.
+
+Material Components' visual style is based on the material design
+specification, developed by a team of iOS engineers and UX designers at Google.
+http://www.google.com/design/spec/material-design/introduction.html
+
+Local Modifications:
+None