Add basic documentation on projects (#1589)

Add basic documentation on projects

user_manual/files/index.rst

@@ -16,4 +16,5 @@ Files & synchronization
    large_file_upload
    quota
    version_control
+   projects
 

user_manual/files/projects.rst

@@ -0,0 +1,35 @@
+========
+Projects
+========
+
+Users can associate files, chats and other items with each other in projects. The various apps will present these items in a list, allowing users to immediately jump to them. Projects are Nextcloud wide. When a user shares a file that is part of a project, the share recipient can see that project, too. A click on any of the items in a project leads right to it, be it a chat, a file or a task.
+
+Create a new project
+--------------------
+
+A new project can be created by linking two items together. Start off by opening a file or folders sharing sidebar. 
+
+.. figure:: ../images/projects1.png
+
+Click *Add to a project* and select the type of item you want to link with the current file/folder. A selector will open that allows you selecting a Talk conversation for example.
+
+.. figure:: ../images/projects2.png
+
+Once the item has been selected a new project is being created and listed in the sharing tab of the sidebar. The same project will also appear in the sharing sidebar of the linked items.
+
+.. figure:: ../images/projects3.png
+
+The list entry shows quick links to a limited number of items. By opening the context menu, the project can be renamed and the full list of items can be expanded.
+
+
+Adding more entries to a project
+--------------------------------
+
+If another item should be added to an already existing project this can be done by searching for the project name in the *Add to a project* picker.
+
+.. figure:: ../images/projects4.png
+
+Visibility of projects
+----------------------
+
+Projects do not influence the access and visibility of the different items. Users will only see projects of other users if they have access to all contained items.