Adding headers for readability.

Author: kevinleung23

README.md

@@ -74,6 +74,8 @@ Doccano can be deployed to AWS ([Cloudformation](https://docs.aws.amazon.com/AWS
 
 ## Installation
 
+### Clone repository
+
 First of all, you have to clone the repository:
 
 ```bash
@@ -87,6 +89,8 @@ _Note for Windows developers: Be sure to configure git to correctly handle line
 git clone https://github.com/chakki-works/doccano.git --config core.autocrlf=input
 ```
 
+### Install doccano
+
 To install doccano, there are three options:
 
 #### Option 1: Pull the production Docker image