Add and Sub int8 and uint8 implementation

Context

Add And Sub int8 and uint8 implementation were required for quantized onnx models import.

See aidge_onnx issues: aidge_onnx#42

Modified files

• AddImpl_kernels.hpp and SubImpl_Kernels.hpp, added implementation for uint8 and int8;

changed the description

changed the description

requested review from @olivierbichler

added Enhancement ⭐ label

approved this merge request

enabled an automatic merge when all merge checks for bbb4472d pass

mentioned in commit 9e272f0c

merged