add readme

Author: nsnguyen

Diff for: README.md

@@ -1 +1,23 @@
 # PHP dotenv-vault
+
+
+<img src="https://raw.githubusercontent.com/motdotla/dotenv/master/dotenv.svg" alt="dotenv-vault" align="right" width="200" />
+
+## Installation
+
+```shell
+composer require dotenv-org/phpdotenv-vault
+```
+
+As early as possible in your application bootstrap process, load .env:
+
+```php
+
+use DotenvVault\DotenvVault;
+require __DIR__.'/vendor/autoload.php';
+
+$dotenv = DotenvVault::createImmutable(__DIR__, '.env.vault');
+$dotenv->load(); # take environment variables from .env.vault
+
+```
+