pipreqs should not be case sensitive

[wurmmi]

We should handle all package names in lowercase, since pip is case insensitive.

• see PEP-426 (https://peps.python.org/pep-0426/#name)
• see PEP-508 (https://peps.python.org/pep-0508/#names)

This will also reduce the amount of mappings. Many of them only match the names to upper-/lowercase.