Fix binary grammar definition of the branch hints custom section (#12)

* Fix binary grammar definition of the branch hints custom section

The overall section structure definition wasm missing.

Author: yuri91

document/core/appendix/custom.rst

@@ -184,6 +184,8 @@ Value  Meaning
 
 .. math::
    \begin{array}{llclll}
+   \production{branch hints section} & \Bbranchhintssec &::=&
+     \Bsection_0(\Bvec(\Bfuncbranchhints)) \\
    \production{function branch hints} & \Bfuncbranchhints &::=&
      \Bfuncidx~\hex{00}~\Bvec(\Bbranchhint) \\
    \production{branch hint} & \Bbranchhint &::=&

document/core/util/macros.def

@@ -1050,6 +1050,7 @@
 
 .. Branch Hints Section, non-terminals
 
+.. |Bbranchhintssec| mathdef:: \xref{appendix/custom}{binary-branchhintssec}{\B{branchhintssec}}
 .. |Bfuncbranchhints| mathdef:: \xref{appendix/custom}{binary-branchhintssec}{\B{funcbranchhints}}
 .. |Bbranchhint| mathdef:: \xref{appendix/custom}{binary-branchhintsec}{\B{branchhint}}
 .. |Bbranchhintkind| mathdef:: \xref{appendix/custom}{binary-branchhintsec}{\B{branchhintkind}}