Update collaboration doc

Add some diagrams

script/generate-doc-diagrams

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# Install the `plantuml` utility if it is not already installed.
+if [[ -x plantuml ]]; then
+  brew install plantuml
+fi
+
+# Generate SVGs from all of the UML files.
+plantuml      \
+  -nometadata \
+  -overwrite  \
+  -tsvg       \
+  -o ../svg   \
+  docs/diagrams/src/*