Add nitrous oxide synthesis reaction (#22774)

Co-authored-by: whateverusername0 <whateveremail>
Co-authored-by: Kevin Zheng <kevinz5000@gmail.com>

Content.Shared/Atmos/Atmospherics.cs

@@ -241,6 +241,11 @@ namespace Content.Shared.Atmos
         /// </summary>
         public const float MiasmicSubsumationMaxConversionRate = 5f;
 
+        /// <summary>
+        ///     Divisor for Miasma Oxygen reaction so that it doesn't happen instantaneously.
+        /// </summary>
+        public const float MiasmaOxygenReactionRate = 10f;
+
         /// <summary>
         ///     Determines at what pressure the ultra-high pressure red icon is displayed.
         /// </summary>