feat: improve ss58 encoding/decoding

[kratico]

Resolves #619

Add ss58 encoding and decoding for different payload and checksum lengths (see ss58-format).

Note: MultiAdress.Index use formats whose checksum length is 1 provided that the index is of type u8, u16, u32 or u64 (1, 2, 4 or 8 byte payload).

[kratico]

These libs support 33 byte payload with 2 byte checksum

• https://github.com/polkascan/py-scale-codec/blob/master/scalecodec/utils/ss58.py#L121
• https://github.com/wyhaines/base58.cr/blob/main/src/base58/ss58.cr#L284

[tjjfvi]

Note: MultiAdress.Index use formats whose checksum length is 1 provided that the index is of type u8, u16, u32 or u64 (1, 2, 3 or 4 byte payload).

It would be 1/2/4/8 byte payload, no?

[kratico]

Note: MultiAdress.Index use formats whose checksum length is 1 provided that the index is of type u8, u16, u32 or u64 (1, 2, 3 or 4 byte payload).

It would be 1/2/4/8 byte payload, no?

Yes!

[tjjfvi]

Could we get a test for every valid address length and every valid payload length to make sure they always round-trip correctly?

[kratico]

Could we get a test for every valid address length and every valid payload length to make sure they always round-trip correctly?

I could add decoding tests for the 16 formats.
But for encoding, I will need to change the encode(...) signature to accept the desired checksum or I can leave it as is.
@tjjfvi WDYT?