feat(strcmp): adding the function strcmp function

This function is already commented

src/ft_strcmp.s

@@ -0,0 +1,29 @@
+segment .note.GNU-stack
+
+section .text
+	global ft_strcmp
+
+ft_strcmp:
+	xor eax, eax						; init to 0
+	xor edx, edx						; init to 0
+	cmp rdi, 0							; check s1 NULL
+	je .exit							; exit if true
+	cmp rsi, 0							; check s2 NULL
+	je .exit							; exit if true
+	jmp .loop							; go to the loop
+
+.loop:
+	movzx ecx, BYTE [rdi + rdx]			; move and change all previous bytes to 0 (zero extanded)
+	movzx r8d, BYTE [rsi + rdx]			; move and change all previous bytes to 0 (zero extanded)
+	mov r9d, ecx						; tmp value
+	or r9b, r8b							; check if one of byte is NULL
+	je .exit							; exit if it's true
+	inc rdx								; counter + 1
+	cmp cl, r8b							; compare les 2 bytes lu (cl end of ecx 2 last bytes)
+	je .loop							; loop again if it's true
+	movzx eax, r8b						; move and change all previous bytes to 0 (zero extanded)
+	sub ecx, eax						; ecx - eax (r8b)
+	mov eax, ecx						; move the ecx in the return value
+
+.exit:
+	ret									; return rax value