A small enhancement: discovering the issue(s) the contributor's commit(s) closes, and linking to those issues too.

e.g.

```
This release contains contributions from many people at Google, as well as:

* Jane Doe: #1234 Fixes foo bug, #1235 Added bar feature
* John Doe: #1236 Improved baz performance
``` @jin Currently we're not linking individual contributors to single issues, just listing everyone who contributed. I'm not sure trying to do that is going to be useful in the release notes: anyone who is interested can check the Git history themselves.
Release note generator should add contributors list
Currently, we're manually adding the list of contributors to thank to the release notes: we should instead be generating this.

Current script:
```
git log <previous version baseline>..<current version baseline> --format="%aN <%aE>" | sort | uniq | grep -v 'google\.com' | cut -d '<' -f 1
```
scripts/release/relnotes.sh
scripts/release/relnotes.sh
diff --git a/scripts/release/relnotes.sh b/scripts/release/relnotes.sh
index c1598c6f50aec6..6557cefe23c214 100755
--- a/scripts/release/relnotes.sh
+++ b/scripts/release/relnotes.sh
@@ -124,8 +124,9 @@ function __format_release_notes() {
 # Create the release notes since commit $1 ($2...${[#]} are the cherry-picks,
 # so the commits to ignore.
 function __release_notes() {
+  local last_release=$1
   local i
-  local commits=$(__get_release_notes_commits $@)
+  local commits=$(__get_release_notes_commits $last_release)
   local length="${#RELNOTES_TYPES[@]}"
   __generate_release_notes "$commits"
   for (( i=0; $i < $length; i=$i+1 )); do
@@ -140,6 +141,17 @@ function __release_notes() {
       echo
     fi
   done
+
+  # Add a list of contributors to thank.
+  local external_authors=$(git log $last_release..HEAD --format="%aN <%aE>" \
+    | sort \
+    | uniq \
+    | grep -v "google.com" \
+    | sed -e 's/[[:space:]]$//' \
+    | tr '\n' ',' \
+    | sed -e 's/,$/\n/' \
+    | sed -e 's/,/, /g')
+  echo "This release contains contributions from many people at Google, as well as ${external_authors}."
 }
 
 # A wrapper around all the previous function, using the CHANGELOG.md
