Add alt texts

Co-authored-by: Derk-Jan Karrenbeld <[email protected]>

Author: SaschaMann

exercises/killer-sudoku-helper/description.md

@@ -20,7 +20,7 @@ In a 3-digit cage with a sum of 7, there is only one valid combination: 124.
 - 1 + 2 + 4 = 7
 - Any other combination that adds up to 7, e.g. 232, would violate the rule of not repeating digits within a cage.
 
-![https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example1.png](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example1.png)
+![Sudoku grid, with three killer cages that are marked as grouped together. The first killer cage is in the 3×3 box in the top left corner of the grid. The middle column of that box forms the cage, with the followings cells from top to bottom: first cell contains a 1 and a pencil mark of 7, indicating a cage sum of 7, second cell contains a 2, third cell contains a 5. The numbers are highlighted in red to indicate a mistake. The second killer cage is in the central 3×3 box of the grid. The middle column of that box forms the cage, with the followings cells from top to bottom: first cell contains a 1 and a pencil mark of 7, indicating a cage sum of 7, second cell contains a 2, third cell contains a 4. The third killer cage follows the outside corner of the central 3×3 box of the grid. It is made up of the following three cells: the top left cell of the cage contains a 2, highlighted in red, and a cage sum of 7. The top right cell of the cage contains a 3. The bottom right cell of the cage contains a 2, highlighted in red. All other cells are empty.](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example1.png)
 
 ## Example 2: Cage with several combinations
 
@@ -31,7 +31,7 @@ In a 2-digit cage with a sum 10, there are 4 possible combinations:
 - 37
 - 46
 
-![https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example2.png](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example2.png)
+![Sudoku grid, all squares empty except for the middle column, column 5, which has 8 rows filled. Each continguous two rows form a killer cage and are marked as grouped together. From top to bottom: first group is a cell with value 1 and a pencil mark indicating a cage sum of 10, cell with value 9. Second group is a cell with value 2 and a pencil mark of 10, cell with value 8. Third group is a cell with value 3 and a pencil mark of 10, cell with value 7. Fourth group is a cell with value 4 and a pencil mark of 10, cell with value 6. The last cell in the column is empty.](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example2.png)
 
 ## Example 3: Cage with several combinations that is restricted
 
@@ -42,7 +42,7 @@ In a 2-digit cage with a sum 10, where the column already contains a 1 and a 4,
 
 19 and 46 are not possible due to the 1 and 4 in the column according to standard Sudoku rules.
 
-![https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example3.png](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example3.png)
+![Sudoku grid, all squares empty except for the middle column, column 5, which has 8 rows filled. The first row contains a 4, the second is empty, and the third contains a 1. The 1 is highlighted in red to indicate a mistake. The last 6 rows in the column form killer cages of two cells each. From top to bottom: first group is a cell with value 2 and a pencil mark indicating a cage sum of 10, cell with value 8. Second group is a cell with value 3 and a pencil mark of 10, cell with value 7. Third group is a cell with value 1, highlighted in red, and a pencil mark of 10, cell with value 9.](https://media.githubusercontent.com/media/exercism/v3-files/main/julia/killer-sudoku-helper/example3.png)
 
 ## Trying it yourself