Add user docs to the navigation

Signed-off-by: Julius Härtl <jus@bitgrid.net>

docs/User_documentation_en.md

@@ -0,0 +1,69 @@
+## Introduction
+### What about Deck ?
+You may know Kanban website like Trello ? Deck is about the same thing but secured and respectful of your privacy !  
+Integrated in Nextcloud, you can easily manage your projects while having your data secured.
+
+### Use cases
+Project management, time management or ideation, Deck makes it easier for you to manage your work.
+
+## Using Deck
+Overall, Deck is easy to use. You can create boards, add users, share the Deck, work collaboratively and in real time.
+
+1. [Create my first board](#1-create-my-first-board)
+2. [Create stacks and cards](#2-create-stacks-and-cards)
+3. [Handle cards options](#3-handle-cards-options)
+4. [Archive old tasks](#4-archive-old-tasks)
+5. [Manage your board](#5-manage-your-board)
+
+### 1. Create my first board
+In this example, we're going to create a board and share it with an other nextcloud user.
+
+![Gif for creating boards](resources/gifs/EN_create_board.gif)
+
+
+### 2. Create stacks and cards
+Stacks are simply columns with list of cards. It can represent a category of tasks or an y step in your projects for example.   
+**Check this out :**
+
+![Gif for creating columns](resources/gifs/EN_create_columns.gif)
+
+What about the cards? Cards are tasks, objects or ideas that fit into a stack. You can put a lot of cards in a stack! An infinity? Who knows! Who knows!   
+
+And all the magic of this software consists on moving your cards from a stack to an other.  
+**Check this out :**
+
+![Gif for creating tasks](resources/gifs/EN_create_task.gif)
+
+### 3. Handle cards options
+Once you have created your cards, you can modify them or add options by clicking on them. So, what are the options? Well, there are several of them:
+- Tag Management
+- Assign a card to a user (s·he will receive a notification)
+- Render date, or deadline
+
+![Gif for puting infos on tasks](resources/gifs/EN_put_infos.gif)
+
+And even :
+
+- Description in markdown language
+- Attachment - *you can leave a document, a picture or some other bonus like that.*
+
+![Gif for puting infos on tasks 2](resources/gifs/EN_put_infos_2.gif)
+
+### 4. Archive old tasks
+Once finished or obsolete, a task could be archived. The tasks is not deleted, it's just archived, and you can retrieve it later
+
+![Gif for puting infos on tasks 2](resources/gifs/EN_archive.gif)
+
+### 5. Manage your board
+You can manage the settings of your Deck once you are inside it, by clicking on the small wheel at the top right.
+Once in this menu, you have access to several things:
+- Sharing
+- Tags
+- Deleted objects
+- Timeline
+
+The **sharing tab** allows you to add users or even groups to your boards.  
+**Tags** allows you to modify the tags available for the cards.  
+**Deleted objects** allows you to return previously deleted stacks or cards.  
+The **Timeline** allows you to see everything that happened in your boards. Everything!
+