feat(#47): extract step

[h1alexbel]

In this pull, I've implemented extract headings step, outlined in Method section.

closes #47
History:

• feat(extract step #47): just extract
• feat(extract step #47): drop readme_text
• feat(extract step #47): extract headings
• feat(extract step #47): remove repos without heading
• feat(extract step #47): no all
• feat(extract step #47): remove stop words
• feat(extract step #47): howto
• feat(extract step #47): extract
• feat(extract step #47): removes_stop_words
• feat(extract step #47): lemmatizes_heading
• feat(extract step #47): filtes
• feat(extract step #47): finds_top_3
• feat(extract step #47): extract step

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PR-Codex overview

This PR introduces a new feature to extract and process headings from README files, including stop words removal, lemmatization, and finding common words.

Detailed summary

• Added a task to extract and process headings from README files
• Implemented functions for stop words removal, lemmatization, and filtering
• Added tests for extracting and processing README headings

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