feat: support reading in from Vec<u8> for file/pdf loaders

[joshua-mo-143]

• I have looked for existing issues (including closed) about this

Feature Request

Support reading in from Vec<u8> (or other similar type) for file loaders.

This will unlock use cases that either require storing the file in memory using a byte array, or where space is constrained and the user would be unable to store the file locally.

Motivation

Anywhere where the user would not be able to store the file on-disk and need to store it in memory as a byte array.

Proposal

Potentially, a new generic trait that allows for loading in of a Vec<u8> using the given libraries.

Do we want to refer to #161 ?

Alternatives

none