Adds base32 encode/decode support

[xikaos]

Issue

#863

Summary

Add base32 encode/decode to gleam/bit_array to complement existing base16/base64 (RFC 4648).

Works on Erlang and JavaScript targets.

Changes

Public API

• base32_encode(input: BitArray, padding: Bool) -> String
• base32_decode(encoded: String) -> Result(BitArray, Nil)

FFI

Erlang: base_encode32/2, base_decode32/1
JavaScript: encode32(bit_array, padding), decode32(s)

Tests

base32_encode_test and base32_decode_test (RFC 4648 vectors, partial-bit, lowercase acceptance, invalid inputs)

Behavior

• Alphabet: A–Z, 2–7 (RFC 4648)
• Encoding: optional = padding; pads bit arrays to full bytes
• Decoding: accepts upper/lowercase and missing padding; rejects invalid chars and interior =

Notes

• No breaking changes; naming aligns with existing base encoders.
• All tests pass on Erlang and JavaScript (Deno) targets.

Additional Notes

• This is my first significant Gleam contribution, please feel free to provide feedback and let me know about any issues.