Filter podcast by phrase or regular expresion present in podcast title or description

### What problem does this address?

When creating a filter for a podcast you can filter it by `Episode Status`, `Release Date`, etc.

I would like to filter podcasts by a `phrase` or `regular expression` in the podcast title or description.it

### What is your proposed solution?

In the `Create Filter` screen add an option to insert a text of regular expression.

Every time a new episode is retrieved the app should verify if the podcast has the text or regular expression of the filter

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

Start by reviewing the Create Filter screen and the existing episode retrieval and podcast-filtering flow. Determine how filter criteria are stored and evaluated, then define behavior for phrase and regular-expression matches against podcast titles and descriptions. Done means a user can configure the text criterion and newly retrieved episodes are filtered accordingly, with coverage for both matching modes.

Written by the indexing model from the issue text.