IHF: Email helpers docs added.

Author: dmitry-ivanov

README.md

@@ -28,6 +28,10 @@ Provides Laravel-specific and pure PHP helper functions.
 - [Dump](#dump)
     - [get_dump](#get_dump)
 
+- [Email](#email)
+    - [is_email](#is_email)
+    - [to_rfc2822_email](#to_rfc2822_email)
+
 - [Format](#format)
     - [format_bytes](#format_bytes)
 
@@ -91,6 +95,17 @@ $dump = get_dump($var);
 // ]
 ```
 
+## Email
+
+#### `is_email()`
+
+Checks if specified string is valid email address or not:
+```php
+$isEmail = is_email('john.doe@example.com');
+
+// true
+```
+
 ## Format
 
 #### `format_bytes()`