docs: clarify method to test if a binary number is a power of two

- Updated README.md to provide a clearer explanation for testing powers of two in binary.
- Replaced the previous answer with a more descriptive method.

Author: Iswanna

number-systems/README.md

@@ -35,7 +35,7 @@ How many bits would you need in order to store the numbers between 0 and 1000 in
 Answer: 10 bits
 
 How can you test if a binary number is a power of two (e.g. 1, 2, 4, 8, 16, ...)?
-Answer: 2^n
+Answer: It can be tested if one of the bits in the value is one e.g 0100, 10, 100
 
 Convert the decimal number 14 to hex.
 Answer: E