Update README.md

Author: XmasApple

README.md

@@ -40,6 +40,7 @@ await driver.Initialize(); // Make sure to await driver initialization
 YDB SDK provides two standard ways for authentication:
 1) `Ydb.Sdk.Auth.AnonymousProvider`. Anonymous YDB access, mainly for tests purposes.
 2) `Ydb.Sdk.Auth.TokenProvider`. Token authentication for OAuth-like tokens.
+3) `Ydb.Sdk.Auth.StaticCredentialsProvider`. Username and password based authentication.
 
 For Yandex.Cloud specific authentication methods, consider using **[ydb-dotnet-yc](https://github.com/ydb-platform/ydb-dotnet-yc)**.