Convert currents examples with specific backend dependencies into demos

[mathieuLivebardon]

Context

Some examples need a specific backend in order to work correctly.
Notably examples with sparql features.

Solutions

1. Create a docker-compose for deploy ud-viz examples with theirs services dependencies.
2. Examples that need a different backend than the one written in ud-viz monorepo (bin/backend.js) should be converted into demos, and then add to the VCity's public list of demos.

Option 2 seems to be the best, cause ud-viz examples work indepently of other backends and it lightens the package.