Use a specific TextFixerConfig instance to control ftfy's text fixing process.

[cary-rowen]

Link to issue number:

Fixed #297

Summary of the issue:

ftfy was incorrectly modifying Chinese punctuation and other text due to aggressive normalization and unwanted fixes, impacting readability.

Description of how this pull request fixes the issue:

This PR adjusts ftfy's configuration to prevent incorrect text modifications:

• Normalization changed from NFKC to NFC to avoid over-aggressive character replacements.
• fix_character_width, uncurl_quotes, fix_latin_ligatures, and unescape_html are now disabled.
• These changes are applied to plain_text, pdf, fitz, and StructuredHtmlParser for consistent text processing.

This prevents ftfy from unintentionally altering punctuation, ligatures, quotes, and HTML entities.

Testing performed:

• Verified that Chinese full-width punctuation (e.g., ，。、“”‘’ ) remains unchanged in plain_text, pdf, and StructuredHtmlParser output.
• Confirmed that NFC normalization is used, preventing over-aggressive text changes.

Known issues with pull request:

No known issues. Further testing and review are welcome.