Add Info about ledger-filecoin-js features for developers

[eshon]

https://github.com/Zondax/ledger-filecoin-js?tab=readme-ov-file#available-commands

"Sign arbitrary amount of raw_bytes" was added to the Filecoin Ledger app to enable proving ownership of a private key. It needs some kind of prefix to indicate it's raw bytes.

Prefix has to be "Filecoin Sign Bytes:\n" + raw_bytes_data" see https://github.com/Zondax/ledger-filecoin/blob/main/tests_zemu/tests/standard.test.ts#L462-L464 and max size is 1MB

Related:

• https://github.com/Zondax/ledger-filecoin/pull/130
• https://github.com/Zondax/ledger-filecoin/issues/118
• Test example: https://github.com/Zondax/ledger-filecoin/blob/main/tests_zemu/tests/standard.test.ts#L363