allow to filter entries by title per subscription

[sebhoss]

fixes #6

[sebhoss]

@tulir sorry missed that there were lint errors - I hope that those are fixed now..

[sebhoss]

Ok sorry again @tulir - third time's a charm? This time I installed all the tools and basically run the entire lint pipeline locally:

• isort ./rss
• black ./rss
• pre-commit run -av trailing-whitespace
• pre-commit run -av end-of-file-fixer
• pre-commit run -av check-yaml
• pre-commit run -av check-added-large-files

All checks are passing locally - sorry again for the inconvenience..