push dev images to dockerhub

[rflechtner]

part of KILTProtocol/ticket#530

This pushes dev images of the demo client to dockerhub with a dedicated tag (develop). These images are not super useful for local testing though; they are set up to connect to a kilt full node.

Outstanding issue(s):

• Images do not connect because connection config is wrong

How to test:

A successful test run has been triggered by 89307a1 (see here). You can also pull the image from dockerhub (kiltprotocol/demo-client) and run it

Checklist:

• I have verified that the code works
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• I have left the code in a better state
• I have documented the changes (where applicable)

[rflechtner]

I'm having issues if I build the dockerfile locally - when I run it and try to access it on the port I mapped, I get an empty page and an error in the console:

[Error] SyntaxError: Unexpected token '<'
	(anonymous function) (main.bb389772.js:1)

[rflechtner]

this is on hold bc we realised these docker images are not really useful; may remove the demo-client from dockerhub