Nextfixes

Author: stefannikolei

src/ImageSharp/Formats/ImageFormatManager.cs

@@ -83,10 +83,7 @@ public void AddImageFormat(IImageFormat format)
 
         lock (HashLock)
         {
-            if (!this.imageFormats.Contains(format))
-            {
-                this.imageFormats.Add(format);
-            }
+            this.imageFormats.Add(format);
         }
     }
 

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -1938,8 +1938,7 @@ private static bool TryReadTextKeyword(ReadOnlySpan<byte> keywordBytes, out stri
         // Keywords should not be empty or have leading or trailing whitespace.
         name = PngConstants.Encoding.GetString(keywordBytes);
         return !string.IsNullOrWhiteSpace(name)
-            && !name.StartsWith(" ", StringComparison.Ordinal)
-            && !name.EndsWith(" ", StringComparison.Ordinal);
+            && !name.StartsWith(' ') && !name.EndsWith(' ');
     }
 
     private static bool IsXmpTextData(ReadOnlySpan<byte> keywordBytes)