Update preview workflow

Author: honno

.circleci/config.yml

@@ -19,10 +19,10 @@ jobs:
           name: build docs
           no_output_timeout: 25m
           command: |
-            pip install -r requirements.txt
-            sphinx-build -b html -WT --keep-going spec build/draft -d doctrees
+            pip install .[doc]
+            make -C spec/ build
       - store_artifacts:
-          path: build/draft
+          path: spec/_build/
 
 workflows:
   version: 2

.github/workflows/pages.yml

@@ -91,7 +91,7 @@ jobs:
         if: ${{ github.event_name == 'pull_request'}}
         with:
           name: html
-          path: build/
+          path: spec/_build/
           if-no-files-found: error
 
       # Configure Git: