"View on GitHub" is wrong label for non-github repos

[jfowl]

e.g. https://marketplace.pretix.eu/products/pretix-matrix-inviter/ links to a GitLab instance.

Maybe just rename to "View Sourcecode"?

[raphaelm]

To be fair, the input field is called "GitHub URL", so it's more than just a relable of the button ;)