Add base32 encode/decode to standard library

[abs0luty]

Add base32 support to standard library

Motivations

• Base32 (RFC 4648) is a standard peer to base16 and
• Eliminate third-party dependencies when base16/base64 are already part of stdlib.
• Consistent cross-target availability (Erlang and JavaScript).

Proposed API

Public Gleam functions in bit_array:

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

Examples

import gleam/bit_array

// Encode with/without padding
bit_array.base32_encode(<<"foobar":utf8>>, True)  // "MZXW6YTBOI======"
bit_array.base32_encode(<<"foobar":utf8>>, False) // "MZXW6YTBOI"

// Decode (case-insensitive, padding optional)
bit_array.base32_decode("MZXW6YTBOI======") // Ok(<<"foobar":utf8>>)
bit_array.base32_decode("mzxw6ytboi")   

• Thread for Add base32 encode/decode to gleam_stdlib stdlib#863, since the related pull request Adds base32 encode/decode support stdlib#864 was closed due to implementing unplanned changes.