feat: Add dig lookup functionality

[laurynasgadl]

Adds a new method lookup to the dig client, that allows the use of additional options and queries with the dig command.
Example:

$result = $client->lookup(
    $domain,
    $type,
    new DigOptions(
        server: '8.8.8.8',
    ),
    new DigQuery(
        all: false,
        answer: true,
    ),
);

Also, increases the minimum PHP version requirement to 8.1 from 8.0

[MantasPetrauskas93]

lgtm