Fix various typos

Found via `codespell -q 3 -S ./Emby.Server.Implementations/Localization -L allready,doesnt,inh,receivedfrom,whoknows`

src/Jellyfin.Extensions/SplitStringExtensions.cs

@@ -55,7 +55,7 @@ namespace Jellyfin.Extensions
         public static Enumerator Split(this ReadOnlySpan<char> str, char separator) => new(str, separator);
 
         /// <summary>
-        /// Provides an enumerator for the substrings seperated by the separator.
+        /// Provides an enumerator for the substrings separated by the separator.
         /// </summary>
         [StructLayout(LayoutKind.Auto)]
         public ref struct Enumerator

src/Jellyfin.Extensions/StringExtensions.cs

@@ -40,7 +40,7 @@ namespace Jellyfin.Extensions
         }
 
         /// <summary>
-        /// Checks wether or not the specified string has diacritics in it.
+        /// Checks whether or not the specified string has diacritics in it.
         /// </summary>
         /// <param name="text">The string to check.</param>
         /// <returns>True if the string has diacritics, false otherwise.</returns>