Update default API version to v19.0

[wynksaiddestroy]

omniauth-facebook still uses Graph API version 5.0 as the default, which was shut off in February 2022.
The current API version is v19.0. A quick google search didn't yield any changes to the OAuth part of the API. So I assume it's safe to use the current version of the API.
#374 addressed the problem already.
On the side I updated the CI test matrix and removed all unmaintained Ruby versions.

[simi]

Thanks @wynksaiddestroy, would you mind to add Bigdecimal to gemfile to fix head build as well?

[wynksaiddestroy]

Thanks @wynksaiddestroy, would you mind to add Bigdecimal to gemfile to fix head build as well?

Thanks for the quick response ❤️
The gemspec file now includes bigdecimal as a dependency.
I've also simplified the CI workflow further.

[svoop]

Just a friendly heads-up: Thanks for cutting a release soonish, the v13 API won't work after May 28, so it would be nice to have a few days to update. And thanks for this PR, @wynksaiddestroy !

[svoop]

@simi This is getting kind of urgent now. The currently used API version is shut down in less than a week on May 28. Thanks a lot for merging and cutting a release as soon as you can!

[simi]

Thanks for the PR and comments. I'll cut a release soon. 🙏

[simi]

🥳 https://rubygems.org/gems/omniauth-facebook/versions/10.0.0

[svoop]

Great, thanks a bunch, @simi and @wynksaiddestroy !!