Incomplete Handling of YAML Front Matter

[herzi]

Short description

According to the doc-comment for Article.metadata, Ignite supports YAML front matter like Jekyll does. However, that's not true. Looking at the implementation of Article.processMetadata(for:) reveals that the handling is limited to dictionaries with single-line key-pairs with single values (read: neither dictionaries nor arrays are supported).

Steps to Reproduce

Create a file with the following front matter (which is valid YAML):

---
elements: ['fire']
avatars:
  - roku
  - szeto
---
# Markdown Content

Expected behavior

Accessing the properties elements or avatars return a arrays of strings: ["fire"] and ["roku", "szeto"] respectively.

Actual behavior

Accessing the property elements yields a single string: "[\'fire\']", the property avatars is not present in the list of keys of metadata.

Build information

• OS: macOS 26.2 (25C56)
• Editor: Xcode 26.2 (17C52)
• Swift version: Apple Swift version 6.2.3
• Ignite version: 0.6.0
• Tested browsers: n/a (build issue)

Screenshots
n/a

Additional context

I think either of the following approaches is a useful one to allow for more structure in the front matter:

1. Integrate a full YAML parser like Yams
2. Allow API consumers of Ignite to provide a replacement implementation for YAML parsing (so e.g. my project can provide a more sophisticated one based on Yams)