Bring injector window to original position if already open

Show doesn't do anything if it's already hidden; we want to bring it to the front of the screen and then reposition it CenterParent.

NHSE.WinForms/Subforms/PlayerItemEditor.cs

@@ -93,6 +93,8 @@ private void B_Inject_Click(object sender, EventArgs e)
             if (exist != null)
             {
                 exist.Show();
+				exist.BringToFront();
+				exist.CenterToForm(this);
                 return;
             }
 

NHSE.WinForms/Util/WinFormsUtil.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Drawing;
 using System.Linq;
 using System.Windows.Forms;
 
@@ -68,5 +69,17 @@ internal static DialogResult Prompt(MessageBoxButtons btn, params string[] lines
         public static T? FirstFormOfType<T>() where T : Form => (T?)Application.OpenForms.Cast<Form>().FirstOrDefault(form => form is T);
 
         public static void RemoveDropCB(object sender, KeyEventArgs e) => ((ComboBox)sender).DroppedDown = false;
+
+        /// <summary>
+        /// Centers the <see cref="child"/> horizontally and vertically so that its center is the same as the <see cref="parent"/>'s center.
+        /// </summary>
+        /// <param name="child"></param>
+        /// <param name="parent"></param>
+        internal static void CenterToForm(this Control child, Control parent)
+        {
+            int x = parent.Location.X + ((parent.Width - child.Width) / 2);
+            int y = parent.Location.Y + ((parent.Height - child.Height) / 2);
+            child.Location = new Point(Math.Max(x, 0), Math.Max(y, 0));
+        }
     }
 }