Add ability to accept gzip compressed files

[duongvy0112]

issue: https://github.com/Unstructured-IO/community/issues/37

• add optional parameter gz_uncompressed_content_type
• check if file content-type is application/gzip if gz_uncompressed_content_type is not provided
• add FastAPI version default value( UNSTRUCTURED_API_VERSION ) to avoid error
• updated CHANGELOG.md file
• passed make check and make test

[cragwolfe]

Closing this PR for now since it is not actively being worked on. It can be re-opened when the time comes.