docs: headlines added (#7075)

* Update contributing.md

* Update 02_First_steps.md

* Update docs/en/contributing.md

---------

Co-authored-by: Alexandre Alapetite <alexandre@alapetite.fr>

docs/en/contributing.md

@@ -1,3 +1,5 @@
+# Contributor Guidelines
+
 ## Report a bug
 
 Have you found a bug? Don’t panic, here are some steps to report it with ease:

docs/en/users/02_First_steps.md

@@ -1,19 +1,27 @@
+# User Documentation
+
 Learning how to handle a new application is not always easy. We’ve tried to make FreshRSS as intuitive as possible, but you might still need a little help to master the program.
 
 This section will guide you to the pages you need to get started. The order is tailored to newcomers.
 
+## Add Feeds
+
 [After installing the application](../admins/03_Installation.md), the first step is to add some feeds. You have a few options:
 
 1. [Add a feed manually](04_Subscriptions.md#adding-a-feed)
 2. [Import an OPML or JSON file](04_Subscriptions.md#import-and-export)
 3. [Use the bookmarklet](04_Subscriptions.md#use-bookmarklet)
 
+## Reading Views
+
 Once you have added your feeds to FreshRSS, it is time to read them. There are three available reading modes:
 
 1. [The normal view](03_Main_view.md#normal-view) enables you to quickly read new articles
 2. [The global view](03_Main_view.md#global-view) shows you an overview of the status of your feeds in one glance
 3. [The reader view](03_Main_view.md#reader-view) offers you a comfortable reading experience
 
+## Customize
+
 Now that you’ve mastered basic use, it’s time to configure FreshRSS to improve your reading experience. It’s highly configurable, so it’s recommended to play around with them to find a configuration that suits you well. Here are a few resources to help you improve your daily FreshRSS experience:
 
 * [Organize your feeds in categories](04_Subscriptions.md#feed-management)