fix: linter errors

Author: atk

exercises/piecing-it-together/instructions.md

@@ -20,20 +20,22 @@ For this exercise, you may assume square pieces, so that the format can be deriv
 - If it is equal to 1, it's `square`
 - If it is greater than 1, it's `landscape`
 
-# Three examples
+## Three examples
 
-## Portrait
+### Portrait
 
 A portrait jigsaw puzzle comprising 6 pieces of which all are border pieces and none are inside pieces. It has 3 rows and 2 columns. The aspect ratio is 1.5 (3/2).
 
 ![A 2 by 3 jigsaw puzzle](https://camo.githubusercontent.com/bb806ba85321c2b739e882d6f872897150a87134765383e26a47d88bfe0aa7f8/68747470733a2f2f6173736574732e657865726369736d2e6f72672f696d616765732f6578657263697365732f70696563696e672d69742d746f6765746865722f6a69677361772d70757a7a6c652d3278332e737667)
 
-## Square
+### Square
+
 A square jigsaw puzzle with 9 pieces of which all except the centre piece are border pieces. It has 3 rows and 3 columns. The aspect ratio is 1 (3/3).
 
 ![A 3 by 3 jigsaw puzzle](https://camo.githubusercontent.com/499ca9b4913aac4f3ae18eeec392209ac8b360d892b7cb3be5d28cba4075602c/68747470733a2f2f6173736574732e657865726369736d2e6f72672f696d616765732f6578657263697365732f70696563696e672d69742d746f6765746865722f6a69677361772d70757a7a6c652d3378332e737667)
 
-## Landscape
+### Landscape
+
 A landscape jigsaw puzzle with 12 pieces of which 10 are border pieces and 2 are inside pieces. It has 3 rows and 4 columns. The aspect ratio is 1.333333... (4/3).
 
 ![A 4 by 3 jigsaw puzzle](https://camo.githubusercontent.com/45b18efc8524284928bd8cae6bd72b661e1b9a1ca8959fe5131c7985671030a0/68747470733a2f2f6173736574732e657865726369736d2e6f72672f696d616765732f6578657263697365732f70696563696e672d69742d746f6765746865722f6a69677361772d70757a7a6c652d3478332e737667)