fixed readme

Author: Michael Petri

README.md

@@ -4,20 +4,22 @@
 [![Latest Stable Version](https://poser.pugx.org/michaelpetri/typed-input/v)](//packagist.org/packages/michaelpetri/typed-input)
 [![License](https://poser.pugx.org/michaelpetri/typed-input/license)](//packagist.org/packages/michaelpetri/typed-input)
 
-## Installation:
-```
+## Installation
+
+```shell
 composer require michaelpetri/typed-input 
 ```
 
-## Usage:
+## Usage
+
 ```php
 $typedInput = TypedInput::fromInput($input);
 
 echo $typedInput->getOption('my-option')->asNonEmptyString();
 echo $typedInput->getArgument('my-argument')->asInteger();
 ```
 
-## Available methods:
+## Available methods
 
 * `asBoolean`
 * `asBooleanOrNull`
@@ -32,4 +34,4 @@ echo $typedInput->getArgument('my-argument')->asInteger();
 * `asNonEmptyString`
 * `asNonEmptyStringOrNull`
 * `asNonEmptyStrings`
-* `asDateTimeImmutable`
+* `asDateTimeImmutable`