docs: Add section Synchronize with Documents

docs/index.rst

@@ -28,6 +28,7 @@ advanced topics like scripting and application development process.
     sessions
     pin-items
     password-protection
+    synchronize
     writing-commands-and-adding-functionality
     scripting
     command-examples

docs/synchronize.rst

@@ -0,0 +1,54 @@
+Synchronize with Documents
+==========================
+
+This page describes how to keep items in a tab synchronized with files in a
+directory on a disk (or a Dropbox folder).
+
+Configuration
+-------------
+
+.. note::
+
+    On Windows, to enable this feature you need to install "Synchronize"
+    plugin.
+
+Set path synchronization directory for a tab.
+
+1. Open "Preferences" (``Ctrl+P`` shortcut),
+2. go to "Items" tab,
+3. select "Synchronize",
+
+    .. image:: images/synchronize-config.png
+       :scale: 50%
+       :alt: Configure synchronization directory
+
+4. double-click an empty space in **Tab Name** column and enter name of the tab to synchronize,
+5. click the browse button on the same row and select directory for the tab,
+6. click OK to save changes.
+
+Now any items in the synchronized tab will be saved in the directory and
+existing files will show up in the tab even if the tab or a file is created
+later.
+
+Synchronized items can be copied and edited as normal items.
+
+File Types
+----------
+
+Only files with known format can be shown as items. By default
+files with ``.txt`` suffix show up as text items,
+files with ``.html`` suffix show up as formatted text items,
+files with ``.png`` suffix show up as images etc.
+
+To show other files as items you need to set their file suffix in the second
+table in the configuration. Here you can set icon and MIME format for the file
+data.
+
+    .. image:: images/synchronize-formats.png
+       :scale: 50%
+       :alt: Configure file formats to show
+
+The configuration in the image above allows for content of all files with
+``.cpp`` suffix in synchronized directories to show up text items, i.e. items
+have ``text/plain`` format containing the file data.
+