ci: run prettier before opening docs PR (#1008)

Author: kenjenkins

scripts/open-docs-pull-request.sh

@@ -18,6 +18,7 @@ git clone --depth 1 \
 echo "Copying contents to git repo"
 cp -R "$source_path" "$clone_dir/$destination_path"
 cd "$clone_dir"
+yarn && yarn prettier --write "$destination_path/$source_path"
 git checkout -b "$destination_head_branch"
 
 if [ -z "$(git status -z)" ]; then