factory devfile: should support URL from Github

Describe the bug

Providing a devfile.yaml URL from Github to the Che factory is failling. Che is expecting a raw URL. But it is a common that user provide the Github view URL.

Che version

• latest
• nightly
• other: please specify

Steps to reproduce

1. go to https://github.com/eclipse/che-devfile-registry/tree/master/devfiles/quarkus
2. right click on the devfile.yaml link.
3. copy the link address (should be https://github.com/eclipse/che-devfile-registry/blob/master/devfiles/quarkus/devfile.yaml)
4. paste the link in the Che dashboard (add workspace, url of devfile)
5. the dashboard is failing to load the devfile.

Expected behavior

it should detect that it is github and fetch the raw devfile automatically: https://github.com/eclipse/che-devfile-registry/raw/master/devfiles/quarkus/devfile.yaml

Screenshots

[skabashnyuk]

not reproduced on the latest version 7.26-snapshot.

[skabashnyuk]

Tested with the wrong url. Reopening.