feat: add base32 encoding plugin

[Lalatenduswain]

Summary

Adds a Base32 encoding plugin, completing the encoding family alongside the existing base64, hex, binary, octal, and decimal plugins.

Base32 uses the A-Z2-7 alphabet, so it tokenises differently from Base64 and can slip past guardrails/filters that only account for Base64-style payloads — a distinct obfuscation vector for evaluation.

Changes

• spikee/plugins/base32.py — new plugin, mirrors the structure of base64.py (subclasses Plugin, tagged ENCODING).
• tests/functional/test_spikee_list.py — assert base32 is discoverable via spikee list plugins.
• docs/02_builtin.md — add base32 to the built-in plugins reference table.

Usage

spikee generate --plugins base32

Testing

• spikee list plugins shows base32 under Encoding.
• Verified encode output through spikee's own module loader.
• All functional tests pass locally (test_spikee_list, test_module_loading, and the full test_spikee_generate suite — 113 passed).