Add some inline links to "previous examples"

Fixes #144.

examples/mutexes/mutexes.go

@@ -1,6 +1,6 @@
 // In the previous example we saw how to manage simple
-// counter state using atomic operations. For more complex
-// state we can use a _[mutex](http://en.wikipedia.org/wiki/Mutual_exclusion)_
+// counter state using [atomic operations](atomic-counters).
+// For more complex state we can use a _[mutex](http://en.wikipedia.org/wiki/Mutual_exclusion)_
 // to safely access data across multiple goroutines.
 
 package main

examples/mutexes/mutexes.hash

@@ -1,2 +1,2 @@
-a42e6b574ab2c2bdd38df53d77b9a2f3f3e0b10c
--_LKNceBru
+3ce8467418aa740ea6c930afac3985a943c76311
+kZrod-Rkos

examples/stateful-goroutines/stateful-goroutines.go

@@ -1,6 +1,6 @@
 // In the previous example we used explicit locking with
-// mutexes to synchronize access to shared state across
-// multiple goroutines. Another option is to use the
+// [mutexes](mutexes) to synchronize access to shared state
+// across multiple goroutines. Another option is to use the
 // built-in synchronization features of  goroutines and
 // channels to achieve the same result. This channel-based
 // approach aligns with Go's ideas of sharing memory by

examples/stateful-goroutines/stateful-goroutines.hash

@@ -1,2 +1,2 @@
-9b7362872b9984296fd919441c2b6928ae0d70c1
-qHTT2jOKkS
+603a70a77ed18db9da4f8c7911a92b87fd21400c
+-WqmiTr6ek