Server example

[anttileppa]

As a developer i would like to have a simple example of how to write a server-side implementation for the plugin

[anttileppa]

An example implementation can be found from demo project (https://github.com/foyt/coops-demo) but simpler example would be great

[YingshanDeng]

@anttileppa And how to run the coops-demo locally? thank you!

[anttileppa]

See foyt/coops-demo#35