doc: format doc/api/*.md with markdown formatter

PR-URL: https://github.com/nodejs/node/pull/40403
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

doc/api/embedding.md

@@ -67,6 +67,7 @@ int main(int argc, char** argv) {
 ```
 
 ### Per-instance state
+
 <!-- YAML
 changes:
   - version: v15.0.0