Support Test2 in Test::Mojo

We should support Test2 out of the box, so we can do stuff like this.

use Test2::V0;
use Test2::Mojo;

my $t = Test2::Mojo->new( ... );

$t->get_ok( '/foo' )
    ->status_is(200)
    ->header_is( 'Content-Type' => match qr{application/json} )
    ->json_is( hash {
        field foo => E;
        field bar => DNE;
        end;
    } );

done_testing;