[ADD] inventory: How to do an inventory adjustment with barcodes?

https://docs.google.com/document/d/1iPvjamOehw3O33Jjed8EMzwzPWKsBh29GT2PJsARf3o/edit#

inventory/barcode/operations/adjustments.rst

@@ -1,3 +1,24 @@
 ================================================
 How to do an inventory adjustment with barcodes?
 ================================================
+
+From the Barcode application:
+
+-   Click on **Inventory**
+
+.. image:: media/adjustments01.png
+    :align: center
+
+-   Scan all the products (if you have 5 identical articles, scan it 5
+    times, or use the keyboard to set the quantity).
+
+.. note::
+    If you manage multiple locations, scan the location before scanning the
+    products. Eg. scan a shelf’s barcode ; scan each product on the
+    shelf ; repeat for each shelf in the wharehouse.
+
+-   When you've scanned all the items of the location, validate the
+    inventory manually or by scanning the **Validate** barcode.
+
+.. image:: media/adjustments02.png
+    :align: center