add information about a basic Haskell setup

README.md

@@ -6,4 +6,29 @@ A simple template for Haskell projects built with Stack
 [![License](https://img.shields.io/github/license/pascalpoizat/template-haskell-project.svg?style=flat-square)](LICENSE)
 [![Version](https://img.shields.io/github/tag/pascalpoizat/template-haskell-project.svg?label=version&style=flat-square)](template-haskell-project.cabal)<br/>
 
-documentation to be updated (meanwhile, it has been removed, see earlier versions if needed)
+- documentation to be updated (meanwhile, it has been removed, see earlier versions if needed).
+
+- some language-independent information can be found here: [template-java-project](https://github.com/pascalpoizat/template-java-project).
+
+## Installing the environment
+
+The environment is made up of the [GHC compiler](https://www.haskell.org/ghc/) and a dependency manager / build tool such as [Cabal](https://cabal.readthedocs.io/en/stable/) or [Stack](https://docs.haskellstack.org/en/stable/). Haskell libraries can be found on [Hackage](https://hackage.haskell.org). Stack comes with sets of compatible libraries from Hackage organized in [Long Term Support releases](https://www.stackage.org)(LTS).
+
+Versions we use (at the time of writing):
+
+| GHC | Cabal | Stack | LTS |
+| ---:|   ---:|   ---:| ---:|
+|9.2.5| 3.6.2 | 2.9.1 | 20.5|
+
+Installing the environment is simplified using [GHCup](https://www.haskell.org/ghcup/).
+
+1. install GHCup as [presented here](https://www.haskell.org/ghcup/install/)
+2. install GHC, Cabal and/or Stack using GHCup as [presented here](https://www.haskell.org/ghcup/install/).
+
+*This project requires installing both Cabal and Stack.*
+
+## IDE
+
+A simple (and feature-rich) solution is to use the [Haskell Language Server](https://haskell-language-server.readthedocs.io/en/stable/) (HLS) which can be installed using GHCup as [presented here](https://haskell-language-server.readthedocs.io/en/stable/installation.html#ghcup), and have your IDE work with it.
+
+For [Visual Studio Code]() you can use the [Haskell plugin](https://marketplace.visualstudio.com/items?itemName=haskell.haskell), which is able to download HLS by need for you (indeed, it uses GHCUp for this).