Iterate to `remark-frontmatter`-inspired approach over `gray-matter`

In order to decrease the client payload we want to replace gray-matter with a dynamic import approach so front matter variations (YAML vs. TOML vs. JSON, etc) are load the target parser. See this thread for additional context on the proposed approach.

In the spirit of iteration we're just parsing YAML as a v1 with a clear path to use dynamic imports if/when needed