Added tester and commentary to asm files

ft_read.s

@@ -2,16 +2,16 @@ global ft_read
 extern __errno_location
 
 ft_read:
-	mov eax, 0
+	mov eax, 0 ; move the syscall code of write (0) into eax (syscall register)
 	syscall
-	test rax, rax
-	js .error
-	ret
+	test rax, rax ; check if the syscall failed
+	js .error ; if the syscall failed, jump at .error
+	ret ; else return
 
 .error:
-	mov rdx, rax
-	call __errno_location wrt ..plt
-	neg rdx
-	mov [rax], rdx
-	mov rax, -1
-	ret
+	mov rdx, rax ; save rax (return value) into rdx as a temp value
+	call __errno_location wrt ..plt ; call errno_location (put errno pointer into rax) | wrt ..plt means the address of the function will be defined at runtime (needed for libc)
+	neg rdx ; invert the return value
+	mov [rax], rdx ; *errno_value = rdx
+	mov rax, -1 ; set the return value to -1
+	ret ; return