Update PACKAGE.md to include Llama info (#7104)

* Update PACKAGE.md to include Llama info

* Apply suggestions from code review

Co-authored-by: Eric StJohn <[email protected]>

---------

Co-authored-by: Eric StJohn <[email protected]>

src/Microsoft.ML.Tokenizers/PACKAGE.md

@@ -8,11 +8,18 @@ Microsoft.ML.Tokenizers supports various the implmentation of the tokenization u
 * BPE - Byte pair encoding model
 * English Roberta model
 * Tiktoken model
+* Llama model
 
 ## How to Use
 
 ```c#
 using Microsoft.ML.Tokenizers;
+using System.Net.Http;
+using System.IO;
+
+//
+// Using Tiktoken Tokenizer
+//
 
 // initialize the tokenizer for `gpt-4` model, downloading data files
 Tokenizer tokenizer = await Tokenizer.CreateTiktokenForModelAsync("gpt-4");
@@ -33,6 +40,25 @@ Console.WriteLine($"5 tokens from start: {processedText.Substring(0, trimIndex)}
 IReadOnlyList<int> ids = tokenizer.EncodeToIds(source);
 Console.WriteLine(string.Join(", ", ids));
 // prints: 1199, 4037, 2065, 374, 279, 1920, 315, 45473, 264, 925, 1139, 264, 1160, 315, 11460, 13
+
+//
+// Using Llama Tokenizer
+//
+
+// Open stream of remote Llama tokenizer model data file
+using HttpClient httpClient = new();
+const string modelUrl = @"https://huggingface.co/hf-internal-testing/llama-tokenizer/resolve/main/tokenizer.model";
+using Stream remoteStream = await httpClient.GetStreamAsync(modelUrl);
+
+// Create the Llama tokenizer using the remote stream
+Tokenizer llamaTokenizer = Tokenizer.CreateLlama(remoteStream);
+string input = "Hello, world!";
+ids = llamaTokenizer.EncodeToIds(input);
+Console.WriteLine(string.Join(", ", ids));
+// prints: 1, 15043, 29892, 3186, 29991
+
+Console.WriteLine($"Tokens: {llamaTokenizer.CountTokens(input)}");
+// print: Tokens: 5
 ```
 
 ## Main Types