Add Sieve of Eratosthenes algorithm snippet in C++

snippets/cpp/math-and-numbers/sieve-of-eratosthenes.md

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+---
+title: Sieve of Eratosthenes
+description: Generates all prime numbers up to a given maximum value using an efficient algorithm using bitset.
+author: muriloguizelin
+tags: number-theory, prime, sieve
+---
+
+```cpp
+#include <bitset>
+#include <iostream>
+
+constexpr int MAXN = 1e6 + 1;
+
+consteval auto computeSieve() {
+    std::bitset<MAXN> isPrime;
+    isPrime.set();
+    isPrime[0] = isPrime[1] = false;
+    for (int i = 2; i * i < MAXN; ++i) {
+        if (isPrime[i]) {
+            for (int j = i * i; j < MAXN; j += i) {
+                isPrime[j] = false;
+            }
+        }
+    }
+    return isPrime;
+}
+
+// Usage:
+computeSieve();
+if (isPrime[29]) std::cout << "29 is a prime number!" << std::endl;
+```