Rename and update .devcontainer README

[Mark-Niemeyer]

Check if .devcontainer Readme is up to date and rename it to README.md for rendering on the github webpage.

seerep/.devcontainer/README-devcontainer.md

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	# Devcontainer
	This folder contains all files needed for the development container:
	1. devcontainer.json and postCreateCommand.sh: Instructions for VS Code on how to create the dev container based on
	the previously created image
	2. .vscode: The VS Code settings folder. To be used in the devcontainer to create a out of the box working Intellisense
	## Remote Host
	If you want to use a devcontainer on a remote host add the following to the settings.json of your VS Code config in your
	local workspace and replace the placeholder with your values:
	```
	"docker.host": "ssh://your-remote-user@your-remote-machine-fqdn-or-ip-here",
	```
	Also update the workspace mount to a volume in the [devcontainer.json](devcontainer.json) file:
	```
	"workspaceMount": "source=seerep-ws,target=/home/docker/workspace/src,type=volume",
	```
	Make sure that your SSH agent is running and knows about the keys needed to connect to the remote host. (Following
	instructions copied from [here](https://code.visualstudio.com/docs/remote/containers#_using-ssh-keys))
	1. Adding keys to the SSH agent: `ssh-add $HOME/.ssh/github_rsa`
	2. Starting the SSH Agent once: `eval "$(ssh-agent -s)"`
	3. First, start the SSH Agent in the background by running the following in a terminal: `eval "$(ssh-agent -s)"`
	4. Then add these lines to your `~/.bash_profile` or `~/.zprofile` (for Zsh) so it starts on login:
	```
	if [ -z "$SSH_AUTH_SOCK" ]; then
	# Check for a currently running instance of the agent
	RUNNING_AGENT="`ps -ax | grep 'ssh-agent -s' | grep -v grep | wc -l | tr -d '[:space:]'`"
	if [ "$RUNNING_AGENT" = "0" ]; then
	# Launch a new instance of the agent
	ssh-agent -s &> $HOME/.ssh/ssh-agent
	fi
	eval `cat $HOME/.ssh/ssh-agent`
	fi
	```
	Some information regarding devcontainers:
	- <https://code.visualstudio.com/docs/remote/containers>
	- <https://code.visualstudio.com/docs/remote/create-dev-container>
	- <https://code.visualstudio.com/docs/remote/containers-advanced>
	- <https://code.visualstudio.com/docs/remote/containers-advanced#_developing-inside-a-container-on-a-remote-docker-host>
	- <https://code.visualstudio.com/docs/remote/devcontainerjson-reference>