feat: integrate dotenv for secure credential management, update benchmark scripts to load API credentials from .env file, add .env.example template, and ensure .env is properly gitignored for security

examples/env_example.rs

@@ -0,0 +1,48 @@
+use polyfill_rs::ClobClient;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Load environment variables from .env file
+    dotenv::dotenv().ok();
+    
+    println!("🔧 Environment Configuration Example");
+    println!("===================================");
+    
+    // Check if credentials are available
+    match (
+        std::env::var("POLYMARKET_API_KEY"),
+        std::env::var("POLYMARKET_SECRET"),
+        std::env::var("POLYMARKET_PASSPHRASE"),
+    ) {
+        (Ok(api_key), Ok(secret), Ok(passphrase)) => {
+            println!("✅ All credentials loaded from .env file:");
+            println!("   API Key: {}...{}", &api_key[..8], &api_key[api_key.len()-8..]);
+            println!("   Secret: {}...{}", &secret[..8], &secret[secret.len()-8..]);
+            println!("   Passphrase: {}...{}", &passphrase[..8], &passphrase[passphrase.len()-8..]);
+            
+            // Create client (would normally use these credentials)
+            let client = ClobClient::new_internet("https://clob.polymarket.com");
+            
+            // Test basic connectivity
+            println!("\n🌐 Testing connectivity...");
+            match client.get_server_time().await {
+                Ok(timestamp) => {
+                    println!("✅ Server time: {}", timestamp);
+                    println!("🚀 Ready for authenticated operations!");
+                }
+                Err(e) => {
+                    println!("❌ Connection error: {}", e);
+                }
+            }
+        }
+        _ => {
+            println!("❌ Missing credentials in .env file");
+            println!("📝 Create a .env file with:");
+            println!("   POLYMARKET_API_KEY=your-api-key");
+            println!("   POLYMARKET_SECRET=your-secret");
+            println!("   POLYMARKET_PASSPHRASE=your-passphrase");
+        }
+    }
+    
+    Ok(())
+}