[docs] added pages from user manual

docs/docs.user.ops.inventory.stock_entry.md

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+---
+{
+	"_label": "Stock Entry"
+}
+---
+A Stock Entry is a simple document that lets you record Item movement from a Warehouse, to a Warehouse and between Warehouses.
+
+This can be useful in also tracking:
+
+- Material Issues from Stores
+- Sales and Purchase Returns
+- Production (manufacturing).
+
+We will look into the special features of the Stock Entry later when we discuss Accounting and Manufacturing processes.
+
+To make a Stock Entry you have to go to:
+
+> Stock > Stock Entry
+
+In the Stock Entry you have to update the Items table with all your transactions. For each row, you must enter a “Source Warehouse” or a “Target Warehouse” or both (if you are recording a movement).
+
+> **Note:** To update Stock from a spreadsheet, see Stock Reconciliation.
+