docs: Add a quickstart guide for Llama (#91)

## Description
As discussed internally, adding a quickstart with running LLMs to the
README - #17

### Type of change
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [x] Documentation update (improves or adds clarity to existing
documentation)

### Tested on
- [x] iOS
- [x] Android

### Testing instructions
<!-- Provide step-by-step instructions on how to test your changes.
Include setup details if necessary. -->

### Screenshots
<!-- Add screenshots here, if applicable -->

### Related issues
<!-- Link related issues here using #issue-number -->

### Checklist
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [x] I have updated the documentation accordingly
- [x] My changes generate no new warnings

### Additional notes
<!-- Include any additional information, assumptions, or context that
reviewers might need to understand this PR. -->

Author: chmjkb

README.md

@@ -15,6 +15,52 @@ To run any AI model in ExecuTorch, you need to export it to a `.pte` format. If
 Take a look at how our library can help build you your React Native AI features in our docs:  
 https://docs.swmansion.com/react-native-executorch
 
+
+# 🦙 **Quickstart - Running Llama**  
+
+**Get started with AI-powered text generation in 3 easy steps!**  
+
+### 1️⃣ **Installation**  
+```bash
+# Install the package
+yarn add react-native-executorch
+cd ios && pod install && cd ..
+```
+
+---
+
+### 2️⃣ **Setup & Initialization**  
+Add this to your component file:  
+```tsx
+import { 
+  LLAMA3_2_1B_QLORA, 
+  LLAMA3_2_3B_TOKENIZER,
+  useLLM 
+} from 'react-native-executorch';
+
+function MyComponent() {
+  // Initialize the model 🚀
+  const llama = useLLM({
+    modelSource: LLAMA3_2_1B_QLORA,
+    tokenizerSource: LLAMA3_2_1B_TOKENIZER
+  });
+  // ... rest of your component
+}
+```
+
+---
+
+### 3️⃣ **Run the model!**  
+```tsx
+const handleGenerate = async () => {
+  const prompt = "The meaning of life is";
+  
+  // Generate text based on your desired prompt
+  const response = await llama.generate(prompt);
+  console.log("Llama says:", response);
+};
+```
+
 ## Minimal supported versions
 The minimal supported version is 17.0 for iOS and Android 13.