Docker image is supported

[doskoi]

I have created a docker image that can easily to setup build environment, the repo is here: https://github.com/doskoi/RavenLRS

It has been tested on Docker CE on macOS Mojave and Windows 10 Pro, Linux Mint 19 (apt install docker.io)

You can have some tests, and put this in README to help users to use raven. or fork this into your project.

[doskoi]

@fiam You can use docker image as same as inav to put a build.sh in project, the script is accpet build target as parameter to passthrough to the make CLI.

[fiam]

@doskoi This is definitely very nice. Would you like to submit a PR or would you prefer that I link to your repo from the README?

[doskoi]

Sure, I will send a PR with build script for build firmware with docker, and feel free to update README for advanced usage. Like flashing, monitor, use git to update repo. The examples already in my README.

[doskoi]

Well, because the Dockerfile is included clone raven operation, so if I want to use it inside the raven folder, I need to make some changes.

[doskoi]

I've made the update and tested, now it works via build.sh in raven folder or initialize project via docker commands in empty folder.

Pull request: #40