Add Dockerfile

docs/docker.rst

@@ -0,0 +1,14 @@
+.. docker:
+
+.. highlight:: none
+
+Using with Docker
+=================
+
+A docker container exists for easy access to the ``tinygo`` CLI.
+For example, to compile the blinky example from the root of the repository::
+
+    docker run --rm -v $(pwd):/src tinygo/tinygo build -o /src/blinky.elf -target arduino /src/examples/blinky
+
+Note that you cannot run ``tinygo flash`` from inside the docker container,
+so it is less useful for microcontroller development.