use index from end expressions (#1431)

Author: SimonCropp

src/Humanizer/Localisation/NumberToWords/AfrikaansNumberToWordsConverter.cs

@@ -106,7 +106,7 @@ string Convert(int number, bool isOrdinal)
             }
             else if (isOrdinal)
             {
-                parts[parts.Count - 1] += "ste";
+                parts[^1] += "ste";
             }
 
             var toWords = string.Join(" ", parts);

src/Humanizer/Localisation/NumberToWords/ArmenianNumberToWordsConverter.cs

@@ -135,7 +135,7 @@ string ConvertImpl(long number, bool isOrdinal)
             }
             else if (isOrdinal)
             {
-                parts[parts.Count - 1] += "երորդ";
+                parts[^1] += "երորդ";
             }
 
             var toWords = string.Join(" ", parts);

src/Humanizer/Localisation/NumberToWords/AzerbaijaniNumberToWordsConverter.cs

@@ -95,7 +95,7 @@ public override string ConvertToOrdinal(int number)
                 }
             }
 
-            if (word[word.Length - 1] == 't')
+            if (word[^1] == 't')
             {
                 word = word.Substring(0, word.Length - 1) + 'd';
             }

src/Humanizer/Localisation/NumberToWords/BulgarianNumberToWordsConverter.cs

@@ -130,7 +130,7 @@ static string Convert(long input, GrammaticalGender gender, bool isOrdinal, bool
             }
 
             if (isOrdinal && !string.IsNullOrWhiteSpace(lastOrdinalSubstitution))
-                parts[parts.Count - 1] = lastOrdinalSubstitution;
+                parts[^1] = lastOrdinalSubstitution;
 
             return string.Join(" ", parts);
         }

src/Humanizer/Localisation/NumberToWords/CentralKurdishNumberToWordsConverter.cs

@@ -64,7 +64,7 @@ public override string Convert(long number)
         public override string ConvertToOrdinal(int number)
         {
             var word = Convert(number);
-            return $"{word}{(IsVowel(word[word.Length - 1]) ? "یەم" : "ەم")}";
+            return $"{word}{(IsVowel(word[^1]) ? "یەم" : "ەم")}";
         }
 
         static bool IsVowel(char c) =>

src/Humanizer/Localisation/NumberToWords/EnglishNumberToWordsConverter.cs

@@ -110,7 +110,7 @@ string Convert(long number, bool isOrdinal, bool addAnd = true)
             }
             else if (isOrdinal)
             {
-                parts[parts.Count - 1] += "th";
+                parts[^1] += "th";
             }
 
             var toWords = string.Join(" ", parts);