[Feature]: Full attention block support

[typoverflow]

Prerequisites

• [X] I have tried updating UtilsRL to the newest version.
• [X] I have checked both open and closed issues but found nothing related to my request.

UtilsRL verison when proposing this request

0.3.13

What I am expecting

Add attention block as a basic net structure to UtilsRL. Not sure about its design.

Possible solutions

Maybe implement the attention block as some sort of linear layer, and re-use previous code by passing the attention block as linear_type?

Any additional messages which might help

No response

Urgency

Urgent, will bring significant improvement and should be considered in next main version.