Move fmod runtime export to Plugs/RuntimeExports.cs

Plugs/RuntimeExports.cs

@@ -0,0 +1,18 @@
+using System.Runtime;
+
+namespace RemSox.Plugs;
+
+public static partial class RuntimeExports
+{
+    [RuntimeExport("fmod")]
+    public static double fmod(double x, double y)
+    {
+        if (Math.Abs(y) < double.Epsilon)
+        {
+            return double.NaN;
+        }
+
+        double q = Math.Truncate(x / y);
+        return x - (q * y);
+    }
+}