docs(readme): Fix missing headings introduced in repo upgrade

Author: digitalsadhu

.editorconfig

@@ -11,4 +11,4 @@ trim_trailing_whitespace = true
 insert_final_newline = true
 
 [{*.json,.stylelintrc,.eslintrc,.babelrc}]
-indent_size = 2
+indent_size = 2

README.md

@@ -19,6 +19,7 @@
 
 A module that takes any number of css file entry points and packages them together with meta data before providing them as a readable stream.
 
+## Overview
 
 Given any number of css file paths, for each file path, this module will:
 1. fetch the file at the path
@@ -28,6 +29,7 @@ Given any number of css file paths, for each file path, this module will:
 
 The module provides a readable stream of the resulting objects.
 
+### Output data format
 
 ```js
 {
@@ -44,16 +46,20 @@ The module provides a readable stream of the resulting objects.
 }
 ```
 
+## Installation
 
 ```bash
 npm install asset-pipe-css-writer
 ```
 
+## Usage
 
+### Require the writer
 ```js
 const CssWriter = require('asset-pipe-css-writer')
 ```
 
+### Instantiating the writer
 
 Either pass a path to a single css file:
 ```js
@@ -65,6 +71,7 @@ Or pass an array of paths to css files:
 const writer = new CssWriter(['/path/to/css/file1.css', '/path/to/css/file2.css'])
 ```
 
+### Consuming content from the writer
 
 The writer is a readable stream in object mode so in order to access the data you may register a data handler
 and listen for objects to be passed to the handler: