feat(write): adding '.exit' function

- Coherence with read (other syscall mandatory)

src/ft_write.s

@@ -9,7 +9,7 @@ ft_write:
 	syscall					; call the system call write
 	cmp rax, 0				; check if the return value of syscall
 	jl .error				; jump if the return value is less than 0 
-	ret						; return the value of the syscall
+	jmp .exit				; jump to exit
 
 .error:
 	mov rdi, rax			; stock errno value in rdi
@@ -17,5 +17,7 @@ ft_write:
 	call __errno_location	; rax = &errno
 	mov [rax], edi			; stock the errno return in the address of rax
 	mov rax, -1				; set the value of rax to -1
-	ret						; return with -1 (and errno value)
+	jmp .exit				; jump to exit
 
+.exit:
+	ret						; return rax value