Add doc on pattern detector for overflow
Add doc on pattern detector for overflow

SymbiFlow/yosys,cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,SymbiFlow/yosys,cliffordwolf/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,SymbiFlow/yosys,YosysHQ/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,SymbiFlow/yosys,SymbiFlow/yosys,SymbiFlow/yosys,YosysHQ/yosys,cliffordwolf/yosys,SymbiFlow/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,YosysHQ/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys,SymbiFlow/yosys