ci: add deployment pipeline for production documentation

.drone.yml

@@ -91,7 +91,7 @@
 # ---
 kind: pipeline
 type: docker 
-name: documentation
+name: documentation — development
 node:
   environment: ryali
 trigger:
@@ -112,3 +112,29 @@ steps:
 
     - rm -rf /light_docs_dev/*
     - mv ./html/* /light_docs_dev/
+
+---
+
+kind: pipeline
+type: docker
+name: documentation — production
+node:
+  environment: ryali
+trigger:
+  event:
+  - tag
+
+steps:
+- name: build and deploy
+  image: documentation:latest
+  pull: if-not-exists
+  commands:
+    - pwd
+    - cd docs
+    - mkdir generated
+    - touch generated/changelogs.rst
+    - touch generated/api.rst
+    - sphinx-build -M html . .
+
+    - rm -rf /light_docs/*
+    - mv ./html/* /light_docs/