Readme update (#49)

Author: paulb777

README.md

@@ -6,12 +6,78 @@
 > [!IMPORTANT]
 > If you are using the PaLM SDK for Swift, please see [Developers who use the PaLM SDK for Swift](#developers-who-use-the-palm-sdk-for-swift) for instructions.
 
+The Google AI Swift SDK enables developers to use Google's state-of-the-art generative AI models
+(like Gemini) to build AI-powered features and applications. This SDK supports use cases like:
+- Generate text from text-only input
+- Generate text from text-and-images input (multimodal)
+- Build multi-turn conversations (chat)
+
+For example, with just a few lines of code, you can access Gemini's multimodal capabilities to
+generate text from text-and-image input:
+
+```swift
+let model = GenerativeModel(name: "gemini-pro-vision", apiKey: "YOUR_API_KEY")
+let cookieImage = UIImage(...)
+let prompt = "Do these look store-bought or homemade?"
+
+let response = try await model.generateContent(prompt, cookieImage)
+```
+
+## Try out the sample Swift app
+
+This repository contains a sample app demonstrating how the SDK can access and utilize the Gemini
+model for various use cases.
+
+To try out the sample app, follow these steps:
+
+1.  Check out this repository.\
+`git clone https://github.com/google/generative-ai-swift`
+
+1.  [Obtain an API key](https://makersuite.google.com/app/apikey) to use with the Google AI SDKs.
+
+1.  Open and build the sample app in the `Examples` folder of this repo.
+
+1. Run the app once to ensure the build script generates an empty `GenerativeAI-Info.plist` file
+
+1.  Paste your API key into the `API_KEY` property in the `GenerativeAI-Info.plist` file.
+
+1.  Run the app.
+
+## Logging
+
+To enable additional logging in the Xcode console, including a cURL command and raw stream
+response for each model request, add `-GoogleGenerativeAIDebugLogEnabled` as
+`Arguments Passed On Launch` in the Xcode scheme.
+
+## Command Line Tool
+
+A command line tool is available to experiment with Gemini model requests via Xcode or the command
+line:
+
+1. `open Examples/GenerativeAICLI/Package.swift`
+1. Run in Xcode and examine the console to see the options.
+1. Edit the scheme's `Arguments Passed On Launch` with the desired options.
+
+## Contributing
+
+See [Contributing](https://github.com/google/generative-ai-swift/blob/main/docs/CONTRIBUTING.md)
+for more information on
+contributing to the Google AI Swift SDK.
+
+
 ## Developers who use the PaLM SDK for Swift
 
-​​If you're using the PaLM SDK for Swift, review the information below to continue using the PaLM SDK until you've migrated to the new version that allows you to use Gemini.
+​​If you're using the PaLM SDK for Swift, review the information below to continue
+using the PaLM SDK until you've migrated to the new version that allows you to use Gemini.
 
-- To continue using PaLM models, make sure your app depends on version [`0.3.0`](https://github.com/google/generative-ai-swift/releases/tag/0.3.0) _up to_ the next minor version ([`0.4.0`](https://github.com/google/generative-ai-swift/releases/tag/0.4.0)) of `generative-ai-swift`.
+- To continue using PaLM models, make sure your app depends on version
+[`0.3.0`](https://github.com/google/generative-ai-swift/releases/tag/0.3.0)
+_up to_ the next minor version
+([`0.4.0`](https://github.com/google/generative-ai-swift/releases/tag/0.4.0))
+of `generative-ai-swift`.
 
-- When you're ready to use Gemini models, migrate your code to the Gemini API and update your app's `generative-ai-swift` dependency to version `0.4.0` or higher.
+- When you're ready to use Gemini models, migrate your code to the Gemini API and update your app's
+`generative-ai-swift` dependency to version `0.4.0` or higher.
 
-To see the PaLM documentation and code, go to the [`palm` branch](https://github.com/google/generative-ai-swift/tree/palm).
+To see the PaLM documentation and code, go to the
+[`palm` branch](https://github.com/google/generative-ai-swift/tree/palm).