New M3 Demo App for Master Channel (#1378)

* Added components

* Added test

* Added README

* Run flutter format

* Added all the updated components and tests

* Added README file

* Update README.md

* Add textfields to M3 demo app

* move textfield to exprerimental/

* Update component_screen_test.dart

* Fixed comment: changed sdk version

* Changed all double quotes to single

* Added trailing comma, changed all private fields to public except private state classes

* Added enum for screen selection

* Removed comment for material_3_demo

* Added experimental m3 demo app to master CI pipeline

* fixed failing tests

* Modified the analysis_options.yaml

* Fixed warning

* Ran flutter format command

Co-authored-by: Qun Cheng <quncheng@google.com>
Co-authored-by: hangyu <108393416+hangyujin@users.noreply.github.com>

experimental/material_3_demo/windows/runner/utils.h

@@ -0,0 +1,19 @@
+#ifndef RUNNER_UTILS_H_
+#define RUNNER_UTILS_H_
+
+#include <string>
+#include <vector>
+
+// Creates a console for the process, and redirects stdout and stderr to
+// it for both the runner and the Flutter library.
+void CreateAndAttachConsole();
+
+// Takes a null-terminated wchar_t* encoded in UTF-16 and returns a std::string
+// encoded in UTF-8. Returns an empty std::string on failure.
+std::string Utf8FromUtf16(const wchar_t* utf16_string);
+
+// Gets the command line arguments passed in as a std::vector<std::string>,
+// encoded in UTF-8. Returns an empty std::vector<std::string> on failure.
+std::vector<std::string> GetCommandLineArguments();
+
+#endif  // RUNNER_UTILS_H_