Merge pull request #1572 from chuckha/upgrade-process

📖 Adds a library API change to v2->v3 document

Author: k8s-ci-robot

docs/book/src/providers/v1alpha2-to-v1alpha3.md

@@ -17,7 +17,11 @@
 
 ## Context is now required for `external.CloneTemplate` function.
 
-- Pass a context as first argument to calls to `external.CloneTemplate`.
+- Pass a context as the first argument to calls to `external.CloneTemplate`.
+
+## Context is now required for `external.Get` function.
+
+- Pass a context as the first argument to calls to `external.Get`.
 
 ## Cluster and Machine `Status.Phase` field values now start with an uppercase letter.