doc - explicitly install playwright first

Author: jeremylt

.readthedocs.yml

@@ -13,6 +13,7 @@ build:
     - librsvg2-bin
   jobs:
     post_create_environment:
+      - npm install playwright@latest
       - npm install -g @mermaid-js/mermaid-cli
 
 # Build documentation in the docs/ directory with Sphinx