getNextFuncIndex = (ast, countImportedFunc) => {
	const funcSectionMetadata = t.getSectionMetadata(ast, "func");

	if (funcSectionMetadata === undefined) {
		return t.indexLiteral(0 + countImportedFunc);
	}

	const vectorOfSize = funcSectionMetadata.vectorOfSize.value;

	return t.indexLiteral(vectorOfSize + countImportedFunc);
}
Get next func index
The Func section metadata provide information for implemented funcs
in order to have the correct index we shift the index by number of external
functions.
@param {AST} ast Module's AST
@param {number} countImportedFunc number of imported funcs
@returns {t.Index} - index