docs: add retriever SDG toolkit dev note (#666)

* docs: add retriever SDG toolkit dev note

Signed-off-by: Steve Han <sthan@nvidia.com>

* docs: restyle retriever SDG pipeline diagram

Signed-off-by: Steve Han <sthan@nvidia.com>

* docs: fix retriever SDG pipeline flow order

Signed-off-by: Steve Han <sthan@nvidia.com>

* docs: address retriever SDG dev note review

Signed-off-by: Steve Han <sthan@nvidia.com>

* docs: clarify retriever SDG wording

Signed-off-by: Steve Han <sthan@nvidia.com>

---------

Signed-off-by: Steve Han <sthan@nvidia.com>

Author: shan-nvidia

docs/devnotes/.authors.yml

@@ -7,6 +7,14 @@ authors:
     name: NVIDIA NeMo Data Designer Team
     description: NeMo Data Designer Core Team
     avatar: https://avatars.githubusercontent.com/u/1728152?s=200&v=4
+  sthan:
+    name: Steve Han
+    description: Researcher at NVIDIA
+    avatar: https://avatars.githubusercontent.com/u/150830061?v=4
+  oliverholworthy:
+    name: Oliver Holworthy
+    description: Machine Learning Engineer at NVIDIA
+    avatar: https://avatars.githubusercontent.com/u/1216955?v=4
   dcorneil:
     name: Dane Corneil
     description: Researcher at NVIDIA