Add a URI for the iRail organization

[pietercolpaert]

Make sure that the RDFa and/or JSON-LD snippet on our home page contains the description of iRail as the organization/project and working group of Open Knowledge Belgium

URIs to defined:

• https://irail.be/#org -- the organization that fosters digital creativity concerning mobility
• https://irail.be/#project -- the software project to share data on public transport in Belgium