Add complete AWS credential examples to the allowable patterns

Add short-term and long-term examples:

* ASIAIOSFODNN7EXAMPLE
* ASIAI44QH8DHBEXAMPLE
* AKIAI44QH8DHBEXAMPLE
* je7MtGbClwBF/2Zp9Utk/h3yCo8nvbEXAMPLEKEY

Viewing `git secrets --list` after `git secrets --register-aws` adds these two allowed:

https://github.com/awslabs/git-secrets/blob/5357e18bc27b42a827b6780564ea873a72ca1f01/git-secrets#L242-L243

There are more to be allowed, for example from https://docs.aws.amazon.com/cli/v1/userguide/cli-configure-files.html:

short term:
> ```
> [default]
> aws_access_key_id=ASIAIOSFODNN7EXAMPLE
> aws_secret_access_key=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
> aws_session_token = IQoJb3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZVERYLONGSTRINGEXAMPLE
>
> [user1]
> aws_access_key_id=ASIAI44QH8DHBEXAMPLE
> aws_secret_access_key=je7MtGbClwBF/2Zp9Utk/h3yCo8nvbEXAMPLEKEY
> aws_session_token = fcZib3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZ2luX2IQoJb3JpZVERYLONGSTRINGEXAMPLE```
> ```

long-term:
> ```
> [default]
> aws_access_key_id=AKIAIOSFODNN7EXAMPLE
> aws_secret_access_key=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
>
> [user1]
> aws_access_key_id=AKIAI44QH8DHBEXAMPLE
> aws_secret_access_key=je7MtGbClwBF/2Zp9Utk/h3yCo8nvbEXAMPLEKEY
> ```