[FEATURE] Add options to filter all posts that don't fulfill a specific condition instead of those that do

[Fakeaccount12312]

• I am requesting a feature.
• I am running the latest version of BDfR
• I have read the Opening an issue

Description

Currently there are two main types of options in bdfr:
Those that add sources to the pool of what is being downloaded, such as --subreddit, --user, --include-id-file, ... and those the filter out any posts meeting specific requirements from this pool, such as --ignore-user, --disable-module, --skip-domain, --skip-subreddit and --skip.
What is missing is an option to filter out all posts that don't fit specific requirements from these sources, e.g. to whitelist conditions instead of blacklisting them, allowing you to only download those posts that are made by a specific user, include a specific domain, from a specific subreddit, ... Right now the only way to do this is to exclude everything else, which only works in certain cases and is not a very clean way to do it.
I'd like to hear what you think about this idea, I've seen some issues/discussions where this could've been useful. Thanks for your work on this tool regardless, I am thankful for it.