Added resumable loading, along with signal handling.

This version can store state after receiving SIGINT.
This is achieved by polling FIFO read state;

IO.hpp

@@ -3,4 +3,9 @@
 #include <cstdint>
 #include <vector>
 
-std::vector<uint8_t> readBytes(const size_t count);
+//Returns either the number of bytes specified,
+//or returns empty vector without discarding bytes from HID stream
+std::vector<uint8_t> readNonBlock(const size_t count);
+
+//Blocking write to HID stream - shouldn't block for too long
+void write(const uint8_t* bytes, const size_t count);