Support python related languages in to_notion_language

[ftnext]

Fix #19

[Copilot]

Pull Request Overview

This PR adds support for Python-related languages in the to_notion_language function by refactoring the language mapping logic and expanding support for additional Pygments language identifiers.

• Moved the to_notion_language function from writers.py to a dedicated module literal_block.py
• Added support for Python-related languages like pycon (Python console) and pytb (Python traceback)
• Introduced comprehensive test coverage for the language mapping functionality

Reviewed Changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/sphinx_notion/nodes/literal_block.py	New module containing refactored to_notion_language function with expanded Python language support
src/sphinx_notion/writers.py	Updated to import to_notion_language from the new module location
tests/nodes/test_literal_block.py	Added comprehensive test coverage for the language mapping function
tests/roots/test-code/source/index.rst	Removed test case for code block without language specification
tests/roots/test-code/expected.json	Updated expected output to match the removed test case

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