fix: Support text files with other encodings than UTF-8

[maozdemir]

Fixes #418 (#415). Fixes #453 As seen in langchain docs: https://github.com/hwchase17/langchain/blob/master/docs/use_cases/question_answering.md

[imartinez]

Maybe we should try this instead @maozdemir https://python.langchain.com/en/latest/modules/indexes/document_loaders/examples/file_directory.html?highlight=TextLoader#c-auto-detect-encodings

[maozdemir]

Maybe we should try this instead @maozdemir https://python.langchain.com/en/latest/modules/indexes/document_loaders/examples/file_directory.html?highlight=TextLoader#c-auto-detect-encodings

Yes, my langchain was on 0.0.171 and apparently that feature was proposed in 0.0.174. Your suggestion works much better. @imartinez