Implement all instructions in emulator

[ed255]

• [ ] lui
• [ ] addi
• [ ] ld
• [ ] sd
• [x] add
• [x] sub
• [x] mul
• [x] divu
• [x] remu
• [x] sltu
• [x] beq @jeong0982
• [x] jal @jeong0982
• [x] jalr @jeong0982
• [ ] ecall

[jeong0982]

I'll implement beq, jal, jalr first.