Improve Railway deployment docs

[Martinsos]

User said following (Discord convo, and also connected convo here):

I would also specify (or remark somehow in the documentation) in part 3 of deploying the server with Railway that the urls you put as WASP_WEB_CLIENT_URL and WASP_SERVER_URL have to have https:// and the url. If not, the app may not work properly (CORS errors for example). This is because when you copy the url from Railway it doesn't have https:// (see picture)

It would also be nice to highlight that (working with railway) all the environment variables (client and server) should be specified before deployment. I had a problem with the client myself because I set the PORT to 8043 (as said in the documentation), but I did it after deployment. Got this error (see picture) all the time and at the end decided to delete the client and set it up again this time specifying the port previous to deployment and worked first try.

[Martinsos]

We did the first thing with #2108 !