Adds missing READMEs to dynamic_theme, gemini_tasks (#2288)

Adds `README.md` files to the dynamic_theme and gemini_tasks projects.
Also removes a block of commented-out code from one of them.

dynamic_theme/README.md

@@ -0,0 +1,21 @@
+# Flutter Dynamic Theme Sample
+
+A developer sample demonstrating how to call on-device Flutter APIs based on
+output from the Gemini API. Allows the user to dynamically change font scale,
+colors, and other theme properties inside a running app using natural language.
+
+## Goals
+
+* Show how to use the Gemini API for a chat session.
+* Demonstrate how to use functions calls with the Gemini API.
+* Show how to tie responses from Gemini to specific local API calls.
+
+## Questions/issues
+
+If you have a general question about any of the techniques you see in
+the sample, Flutter's open source community is a great place to find answers.
+You can find links to online and local groups at
+[https://flutter.dev/community]!
+
+If you run into an issue with the sample itself, please file an issue
+in the [main Flutter repo](https://github.com/flutter/flutter/issues).

dynamic_theme/lib/main.dart

@@ -172,10 +172,6 @@ class _ExampleState extends State<Example> {
     loading.value = true;
     try {
       final prompt = StringBuffer();
-      // prompt.writeln(
-      //   'If the following is not a question assume'
-      //   'it is a new task to be added:',
-      // );
       prompt.writeln(message);
       final response = await callWithActions([Content.text(prompt.toString())]);
       if (response.text != null) {

gemini_tasks/README.md

@@ -0,0 +1,20 @@
+# Flutter Todo List Sample
+
+Developer sample written in Flutter demonstrating how to interact with a to-do
+list in natural language using the Gemini API.
+
+## Goals
+
+* Show how to use the Gemini API for a chat session.
+* Demonstrate how to use functions calls with the Gemini API.
+* Show how to manage the state of a list using Gemini.
+
+## Questions/issues
+
+If you have a general question about any of the techniques you see in
+the sample, Flutter's open source community is a great place to find answers.
+You can find links to online and local groups at
+[https://flutter.dev/community]!
+
+If you run into an issue with the sample itself, please file an issue
+in the [main Flutter repo](https://github.com/flutter/samples/issues).