Update Rust crate comrak to v0.21.0 (#1232)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Cargo.lock

@@ -17,7 +17,7 @@ serde = "=1.0.196"
 serde_derive = "=1.0.196"
 serde_yaml = "=0.9.31"
 serde_json = "=1.0.113"
-comrak = "=0.20.0"
+comrak = "=0.21.0"
 rayon = "=1.8.1"
 regex = "=1.10.3"
 sass-rs = "=0.2.2"