LibCrypto: Add LCM functionality to UnsignedBigInteger

Author: https://github.com/devgianlu
Commit: d55f759bbb
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4950
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/konradekk
Reviewed-by: https://github.com/shannonbooth

Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -80,6 +80,7 @@ public:
     [[nodiscard]] UnsignedDivisionResult divided_by(UnsignedBigInteger const& divisor) const;
     [[nodiscard]] UnsignedBigInteger pow(u32 exponent) const;
     [[nodiscard]] UnsignedBigInteger gcd(UnsignedBigInteger const& other) const;
+    [[nodiscard]] UnsignedBigInteger lcm(UnsignedBigInteger const& other) const;
 
     [[nodiscard]] u32 hash() const;