Fix typo

CONTRIBUTING.md

@@ -1,12 +1,12 @@
 # Contribution guide
 
-## How to participate in a challenge?
+### How to participate in a challenge?
 1. Your contribution should fit on **single HTML file**, no folders, no any other external files even icons or images. You could use inline SVGs or CDN, if it is really necessary.
 2. Navigate to the folder which represents the challenge you want to participate in (`/public/challenge-contributions/THE_NUMBER_OF_THE_CHALLENGE`).
 3. Find the HTML file with your name and write the code you want to contribute. It is named using the first letter of your first name in combination with your last name.
 4. You could use any of the methods described below to access the project.
 
-## How to add my code to the project?
+### How to add my code to the project?
 #### Option 1: Request access to the project
 You could requires access writes to the project then you could use the GitHub UI to upload a HTML file. Alternatively you clone the project locally, create branch and submit your files by opening a PR to master.
 
@@ -17,5 +17,5 @@ You could fork the project and then open PR to the upstream project. Here are co
 * [GitHub Pull Request in 100 Seconds - Git a FREE sticker](https://www.youtube.com/watch?v=8lGpZkjnkt4)
 * [How to make a pull request on an open source project](https://www.youtube.com/watch?v=8A4TsoXJOs8)
 
-## Git, branches, name, strategy...
+### Git, branches, naming, strategy...
 TBD