[docs] new selling pages added

docs/user/selling/docs.user.selling.territory.md

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+{
+	"_label": "Territory"
+}
+---
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+Territory is a place to signify where your customers come from. If you operate in one country, you can give that country name as your Territory. For Example, India, US, or Rest of the World, could be your Territories. If you operate in many locations, ERPNext allows you to create more Territories. You can also have child Territories under parent Territories. This helps in assigning different regions to different sales staff.
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+![Territory Tree](img/territory-tree.png)
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