Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

docs/c-api/mg_util.h/mg_url_encode.md

@@ -0,0 +1,13 @@
+---
+title: "mg_url_encode()"
+decl_name: "mg_url_encode"
+symbol_kind: "func"
+signature: |
+  struct mg_str mg_url_encode(const struct mg_str src);
+---
+
+URL-escape the specified string.
+All non-printable characters are escaped, plus `._-$,;~()/`.
+Input need not be NUL-terminated, but the returned string is.
+Returned string is heap-allocated and must be free()'d. 
+