Add installation instructions

Author: Mitsutoshi Aoe

README.md

@@ -3,3 +3,67 @@
 [![Hackage-Deps](https://img.shields.io/hackage-deps/v/threadscope.svg)](http://packdeps.haskellers.com/feed?needle=threadscope)
 [![Build Status](https://travis-ci.org/haskell/ThreadScope.svg?branch=master)](https://travis-ci.org/haskell/ThreadScope)
 [![Build status](https://ci.appveyor.com/api/projects/status/y6kd8pyh2f3qok4f?svg=true)](https://ci.appveyor.com/project/Mikolaj/threadscope)
+
+## Installation
+
+### Linux
+
+GTK+2 is required to be installed. On Ubuntu-like systems:
+
+```sh
+sudo apt install libgtk2.0-dev
+```
+
+Then you can build threadscope using cabal:
+```sh
+cabal new-build
+```
+
+Or using stack:
+```sh
+stack setup
+stack install
+```
+
+### macOS
+
+GTK+ and gtk-mac-integration are required.
+
+```sh
+brew install gtk+ gtk-mac-integration
+```
+
+Then you can build threadscope using cabal:
+```sh
+cabal new-build --constraint="gtk +have-quartz-gtk"
+```
+
+Or using stack:
+```sh
+stack setup
+stack install --flag gtk:have-quartz-gtk
+```
+
+### Windows
+
+stack is the recommended tool to build threadscope on Windows.
+
+CAVEAT: Currently gtk2 needs to be installed twice: one for stack's MSYS2 environment and another for local MSYS2 environment.
+
+In command prompt:
+```sh
+stack setup
+stack exec -- pacman --needed -Sy bash pacman pacman-mirrors msys2-runtime msys2-runtime-devel
+stack exec -- pacman -Syu
+stack exec -- pacman -Syuu
+stack exec -- pacman -S base-devel mingw-w64-x86_64-pkg-config mingw-w64-x86_64-toolchain mingw-w64-x86_64-gtk2
+stack install
+```
+
+Then in MSYS2 MINGW64 shell:
+```sh
+pacman -S $MINGW_PACKAGE_PREFIX-gtk2
+echo 'export PATH=$APPDATA/local/bin:$PATH' >> .profile
+source .profile
+threadscope
+```