feat: setup dynamic rspec testing / good-bye manual test creation

[gildesmarais]

This pull request introduces dynamic test generation for config files, streamlining the testing process and reducing the need for individual spec files. It also updates several config YAML files to use parameterized sections, and improves documentation and Makefile commands to support the new workflow.

Testing infrastructure improvements:

• Added dynamic test commands (test-config, test-domain, test-debug) and migration helpers (migrate-tests, restore-tests) to the Makefile to support testing individual configs and domains, and to facilitate migration to dynamic tests.
• Removed individual spec files for each config from the spec/html2rss/configs/ directory, as dynamic tests now cover these cases. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

Config file enhancements:

• Updated config YAML files (apnews.com/hub.yml, cnet.com/section_sub.yml, webentwickler-jobs.de/in.yml) to use parameterized sections, allowing for more flexible and reusable configuration. [1] [2] [3]

Documentation updates:

• Added a new section to the README.md explaining dynamic test generation and how to use the new Makefile commands for testing configs and domains, making it easier for contributors to add and test new configs.