change errata format to markdown for better rendering in online git repos

errata → errata.md

@@ -1,3 +1,8 @@
+---
+title: 'Errata and Notes for "Learn Physics with Functional Programming" by Scott N. Walck'
+author: George C. Privon
+---
+
 # Chapter 1
 
 - Exercise 1.4: Until this point, demonstrated functions have a single argument and a single return value. The reader won't see until the start of Chapter 4 (pg 36) that type definitions have a `->` between all types, rather than the arrow separating the arguments from the return values.