added installation instruction to README

Author: Stephan Sahm

README.md

@@ -8,3 +8,19 @@
 This package defines julia implementations for the common types `Option` (aka `Maybe`), `Either` and `Try`, as well as one extra type `ContextManager` which mimics Python's `with`-ContextManager.
 
 For more details check out the [documentation](https://schlichtanders.github.io/DataTypesBasic.jl/dev/).
+
+
+## Installation
+
+The package is soon going to be registered at General, until then you can use it by adding a custom registry.
+```julia
+using Pkg
+pkg"registry add https://github.com/JuliaRegistries/General"  # central julia repository
+pkg"registry add https://github.com/schlichtanders/SchlichtandersJuliaRegistry.jl"  # custom repository
+pkg"add DataTypesBasic"
+```
+
+Use it like
+```julia
+using DataTypesBasic
+```