missing pair export, doc fixes

Author: rayegun

README.md

@@ -75,7 +75,7 @@ If you use SuiteSparseGraphBLAS.jl in your research please cite the following th
   keywords = {GraphBLAS, Graph algorithms, sparse matrices}
 }
 ```
-[pdf](https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9622789&casa_token=VPmmUD8cdFcAAAAA:NYSm3tdjrBwF53rJxo9PqVRWzXY41hE6l1MoKpBqqZC0WESFPGx6PtN1SjVf8M4x01vfPrqU&tag=1)
+[pdf](https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9622789&casa_token=VPmmUD8cdFcAAAAA:NYSm3tdjrBwF53rJxo9PqVRWzXY41hE6l1MoKpBqqZC0WESFPGx6PtN1SjVf8M4x01vfPrqU&tag=1):
 ```bibtex
 @INPROCEEDINGS{9622789,
 author={Pelletier, Michel and Kimmerer, Will and Davis, Timothy A. and Mattson, Timothy G.},

docs/src/index.md

@@ -234,4 +234,5 @@ pages={1-7},
 doi={10.1109/HPEC49654.2021.9622789},
 ISSN={2643-1971},
 month={Sep.}
-}
+}
+```

src/operators/binaryops.jl

@@ -7,7 +7,8 @@ using ..LibGraphBLAS
 export BinaryOp, @binop
 
 export second, rminus, iseq, isne, isgt, islt, isge, isle, ∨, ∧, lxor, xnor, fmod, 
-bxnor, bget, bset, bclr, firsti0, firsti, firstj0, firstj, secondi0, secondi, secondj0, secondj
+bxnor, bget, bset, bclr, firsti0, firsti, firstj0, firstj, secondi0, secondi, secondj0, 
+secondj, pair
 
 struct BinaryOp{F} <: AbstractBinaryOp
     juliaop::F