[ADD] Sales: Introduction to Odoo Sales

https://www.youtube.com/watch?v=VMuCr5_arsY

sales/overview/main_concepts.rst

@@ -5,5 +5,6 @@ Main Concepts
 .. toctree::
    :titlesonly:
 
+   main_concepts/introduction
    main_concepts/terminologies
    main_concepts/invoicing

sales/overview/main_concepts/introduction.rst

@@ -0,0 +1,63 @@
+==========================
+Introduction to Odoo Sales
+==========================
+
+.. youtube:: PWKez0gn6Ts
+    :align: right
+    :width: 700
+    :height: 394
+
+Transcript
+==========
+
+As a sales manager, closing opportunities with Odoo Sales is 
+really simple.
+
+I selected a predefined quotation for a new product line offer. 
+The products, the service details are already in the quotation. 
+Of course, I can adapt the offer to fit my clients needs. 
+
+The interface is really smooth. I can add references, some 
+catchy phrases such as closing triggers (*here, you save $500 
+if you sign the quote within 15 days*). I have a beautiful and 
+modern design. This will help me close my opportunities more 
+easily. 
+
+Plus, reviewing the offer from a mobile phone is easy. 
+Really easy. The customer got a clear quotation with a 
+table of content. We can communicate easily. I identified an 
+upselling opportunity. So, I adapt the offer by adding more 
+products. When the offer is ready, the customer just need to sign 
+it online in just a few clicks. 
+Odoo Sales is integrated with major shipping services: UPS, Fedex, 
+USPS and more. The signed offer creates a delivery order automatically.
+
+That's it, I sucesfully sold my products in just a few clicks.
+
+Oh, I also have the transaction and communication history 
+at my fingertips. It's easy for every stakeholder to know 
+clearly the past interaction. And any information related 
+to the transaction.
+
+-   If you want to show information, I would do it from a customer 
+    form, something like:
+        
+    - Kanban of customers, click on one customer
+        
+    - Click on opportunities, click on quotation
+        
+    - Come back to customers (breadcrum)
+     
+    - Click on customer statement letter
+
+Anytime, I can get an in-depth report of my sales activity. 
+Revenue by salespeople or department. Revenue by category of 
+product, drill-down to specific products, by quarter or month,... 
+I like this report: I can add it to my dashboard in just a click. 
+
+Odoo Sales is a powerful, yet easy-to-use app. At first, I used 
+the sales planner. Thanks to it, I got tips and tricks to boost 
+my sales performance. 
+
+Try Odoo Sales now and get beautiful quotations, amazing dashboards 
+and increase your success rate.