Fix config key for allowed protocols

[willrowe]

dompdf expects camel case instead of snake case for this specific option as seen here.

[angeljqv]

Look at here

[willrowe]

@angeljqv good to know. I guess this can be merged to allow compatible with older versions or the composer constraint should be bumped up once dompdf releases a new version with the change.

[barryvdh]

Rest of the config is also snake_case

[willrowe]

@barryvdh understood, but just to be clear (and in case anyone else runs into this), since the options are passed through directly to Dompdf, the allowed_protocols key will have no effect when using any version of this library prior to v3.

Support for snake case was added in this PR: https://github.com/dompdf/dompdf/pull/3327 and then released in v3 of dompdf/dompdf.

[barryvdh]

oh hmm, that's odd indeed.