LibJS: Add spec comments to Value::to_u8()

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -1009,15 +1009,24 @@ ThrowCompletionOr<i8> Value::to_i8(VM& vm) const
 // 7.1.11 ToUint8 ( argument ), https://tc39.es/ecma262/#sec-touint8
 ThrowCompletionOr<u8> Value::to_u8(VM& vm) const
 {
-    double value = TRY(to_number(vm)).as_double();
-    if (!isfinite(value) || value == 0)
+    // 1. Let number be ? ToNumber(argument).
+    double number = TRY(to_number(vm)).as_double();
+
+    // 2. If number is not finite or number is either +0𝔽 or -0𝔽, return +0𝔽.
+    if (!isfinite(number) || number == 0)
         return 0;
-    auto int_val = floor(fabs(value));
-    if (signbit(value))
+
+    // 3. Let int be the mathematical value whose sign is the sign of number and whose magnitude is floor(abs(ℝ(number))).
+    auto int_val = floor(fabs(number));
+    if (signbit(number))
         int_val = -int_val;
+
+    // 4. Let int8bit be int modulo 2^8.
     auto int8bit = fmod(int_val, NumericLimits<u8>::max() + 1.0);
     if (int8bit < 0)
         int8bit += NumericLimits<u8>::max() + 1.0;
+
+    // 5. Return 𝔽(int8bit).
     return static_cast<u8>(int8bit);
 }