[#270] Add Indigo CLI installation script

Description

Problem: Currently to get started with Indigo, we need to ask the users following its tutorial to do two things:

• install stack
• compile Indigo

This is not ideal, because it requires to read about stack and a lot of patience just to try out even the first, simplest, example.

What we would like for the user instead is to be able to "grab" and/or install Indigo directly without having to jump through hoops.

Solution: Create an indigo installation script that will install stack and Indigo CLI.

Related issue(s)

Resolves #270 (closed) Depends on #269 (closed)

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