Migrating all the map-building documentation to Github.

+ adding links to Youtube tutorials

docs/maps/hosting.md

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+{.section-title.accent.text-primary}
+# Hosting your map
+
+The [Getting Started](.) page proposes to use a "starter kit" that is relying on GitHub pages for hosting the map. This is a fairly good solution as GitHub pages offers a free and performant hosting.
+
+But using GitHub pages is not necessary. You can host your maps on any webserver.
+
+{.alert.alert-warning}
+If you decide to host your maps on your own webserver, you must **configure CORS headers** in your browser to allow access from WorkAdventure.
+
+## Configuring CORS headers
+
+CORS headers ([Cross Origin Resource Sharing](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS)) are useful when a website want to make some resources accessible to another website. This is exactly what we want to do. We want the map you are designing to be accessible from the WorkAdventure domain (`play.workadventu.re`).
+
+### Enabling CORS for Apache
+
+In order to enable CORS in your Apache configuration, you will need to ensure the `headers` module is enabled.
+
+In your Apache configuration file, simply add the following line inside either the `<Directory>`, `<Location>`, `<Files>` or `<VirtualHost>` sections, or within a `.htaccess` file.
+
+    Header set Access-Control-Allow-Origin "*"
+
+### Enabling CORS on another webserver
+
+Check out [enable-cors.org](https://enable-cors.org/server.html) which has detailed instructions on how to enable CORS on many different webservers.