Add micro:bit hello world

Author: dbrattli

.gitignore

@@ -133,3 +133,4 @@ bin
 build
 
 .idea/
+src/**/*.py

examples/microbit/App.fs

@@ -0,0 +1,5 @@
+module App
+
+open Fable.Python.MicroBit
+
+display.scroll("Fable Python!") |> ignore

examples/microbit/MicroBit.fsproj

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+    <GenerateProgramFile>false</GenerateProgramFile>
+    <Author>Dag Brattli</Author>
+    <Copyright>Dag Brattli</Copyright>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="App.fs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="../../src/Fable.Python.fsproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Fable.Core.Experimental" Version="4.0.0-alpha-002" />
+  </ItemGroup>
+</Project>

src/Fable.Python.fsproj

@@ -20,6 +20,8 @@
     <Compile Include="flask/Flask.fs" />
 
     <Compile Include="cognite-sdk/CogniteSdk.fs" />
+
+    <Compile Include="microbit/MicroBit.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="../../Fable/src/Fable.Core/Fable.Core.fsproj" />

src/microbit/MicroBit.fs

@@ -0,0 +1,32 @@
+module Fable.Python.MicroBit
+
+open Fable.Core
+
+/// Micro:Bit stubs for Fable Python
+type IDisplay =
+    /// Clear the display.
+    abstract clear : unit -> unit
+
+    /// Scrolls value horizontally on the display. If value is an integer or
+    /// float it is first converted to a string using str(). The delay
+    /// parameter controls how fast the text is scrolling. If wait is True,
+    /// this function will block until the animation is finished, otherwise the
+    /// animation will happen in the background. If loop is True, the animation
+    /// will repeat forever. If monospace is True, the characters will all take
+    /// up 5 pixel-columns in width, otherwise there will be exactly 1 blank
+    /// pixel-column between each character as they scroll. Note that the wait,
+    /// loop and monospace arguments must be specified using their keyword.
+    abstract scroll : value: string -> unit
+    abstract scroll : value: string * delay: int -> unit
+
+    /// Turn on the display.
+    abstract on : unit -> unit
+
+    /// Turn off the display.
+    abstract off : unit -> unit
+
+    /// Returns true if the display is on.
+    abstract is_on : unit -> bool
+
+[<Import("display", "microbit")>]
+let display: IDisplay = nativeOnly