add test for mid-file UnicodeBOM
add test for mid-file UnicodeBOM

aarvay/libgraphqlparser,aarvay/libgraphqlparser,graphql/libgraphqlparser,graphql/libgraphqlparser,aarvay/libgraphqlparser,graphql/libgraphqlparser,graphql/libgraphqlparser,aarvay/libgraphqlparser,graphql/libgraphqlparser