[docs] added pages from user manual

docs/docs.user.tools.todo.md

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+---
+{
+	"_label": "Assignment and To Do"
+}
+---
+### Assignment
+
+You can assign any transaction to any user by clicking on the “Assign” button on the right hand column and adding a user.
+
+Step 1: Click on the Assign To Button
+
+Step 2: Add the User and other details
+
+This transaction will appear in:
+
+The To-do list of the user whom this is assigned to in “My List” section
+In the “Assigned by me” section of the user who as assigned this activity.
+
+### To Do
+
+To Do is a simple tool where all the activities assigned to you and assigned by you are listed. You can also add your own to-do items in the list.
+
+