Add suport to multiple targets

[fabidick22]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
Add support for multiple targets. Currently, the module accepts a single parameter as target. In some cases, we may have multiple organizations in AWS and we want several of them to have the same policy.

Describe alternatives you've considered
We can deprecate the target variable and create a new one called targets that allos us to send a list of OUs

targets =  [aws_organizations_organizational_unit.my_ou1, aws_organizations_organizational_unit.my_ou2]