Customizable Attribute Name for @selector Lookups

[Rikaelus]

This adds support for an optional DUSK_HTML_ATTRIBUTE setting for attribute names besides "dusk" within HTML.

Benefits

W3C Compliancy

This will provide a way to achieve W3C compliancy as discussed here and specified here with data- prefixes.

DUSK_HTML_ATTRIBUTE=data-dusk

Transition Support

The attribute can be changed easily during transitory periods where there might be multiple testing engines acting against the same website.

Reduced Exposure

This will allow a more generic attribute name to be chosen to prevent exposing the use of Dusk, Laravel, and PHP to the world. This can help reduce the attack surface for hackers.

Backwards Compatibility

Because the absence of the DUSK_HTML_ATTRIBUTE results in the "dusk" default being used, default behavior should be completely unaffected.

Note

This also achieves the goal sought in #1012 but achieves it through customization rather than by adding static support for data-dusk as a simultaneous attribute to dusk. As such it's a little less invasive while also offering greater flexibility.

[taylorotwell]

Here you go: cf04717

[pataar]

Here you go: cf04717

Thanks!