add task numbers (#564)

exercises/concept/bird-watcher/.docs/hints.md

@@ -1,40 +1,40 @@
 # Hints
 
-## Check what the counts were last week
+## 1. Check what the counts were last week
 
 - [Vectors][vectors] are represented in Clojure using square brackets (`[ ]`)
 
-## Check how many birds visited today
+## 2. Check how many birds visited today
 
 - The [`last`][last] function can be used to return the last item in a sequential collection.
 
-## Increment today's count
+## 3. Increment today's count
 
 - The [`update`][update] function can be used to return a new vector with a different element at a given index.
 
 - The [`count`][count] function can be used to find the length of the vector.
 
 - The [`inc`][inc] and [`dec`][dec] functions can be used to increment and decrement integer values.
 
-## Check if there was a day with no visiting birds
+## 4. Check if there was a day with no visiting birds
 
 - The [`every?`][every?] function can be used to check if all items in a collection satisfy a given predicate.
 
 - The [`pos?`][pos?] predicate returns true if a number is greater than zero.
 
 - The [`not`][not] function returns true if an expression evaluates to logical false.
 
-## Calculate the number of visiting birds for the first number of days
+## 5. Calculate the number of visiting birds for the first number of days
 
 - The [`take`][take] function can be used return a sequence of the first n items in a collection.
 
 - The [`reduce`][reduce] function can be used to add a collection of values together.
 
-## Calculate the number of busy days
+## 6. Calculate the number of busy days
 
 - The [`filter`][filter] higher-order function can be used to return a sequence of items in a collection which satisfy a given predicate.
 
-## Check for odd week
+## 7.  Check for odd week
 
 - The [`=`][equality] function can be used to test equality.