* Replaces `load_file` with `load_bytes` in macro
Loading an `AsRef<[u8]>` object is just more flexible than a filestring.
In the end you can just do `std::fs::read(&str)?` as the argument to get
the same behavior, but the reverse is a lot harder.
* updates markdown rust macro test example with new macro syntax
* Adds the `load_file` method back to rust macro
`load_file` was removed preferring `load_bytes`, but then later readded
with the `load_bytes` method as backend
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