Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

docs/c-api/mbuf.h/mbuf_init.md

@@ -0,0 +1,11 @@
+---
+title: "mbuf_init()"
+decl_name: "mbuf_init"
+symbol_kind: "func"
+signature: |
+  void mbuf_init(struct mbuf *, size_t initial_capacity);
+---
+
+Initialises an Mbuf.
+`initial_capacity` specifies the initial capacity of the mbuf. 
+