Upgrade dependencies and clean css backup files during build

Author: unidevel

website/package.json

@@ -3,8 +3,9 @@
     "examples": "docusaurus-examples",
     "start": "docusaurus-start",
     "fix-css": "sed -ibak -e 's/@supports selector(.*11\\.5rem)}}//' ./static/docs/current/_static/sphinx_immaterial_theme.*.css",
+    "clean-cssbak": "rm -f ./static/docs/current/_static/sphinx_immaterial_theme.*.cssbak",
     "build-site": "docusaurus-build",
-    "build": "yarn fix-css; yarn build-site",
+    "build": "yarn fix-css; yarn build-site; yarn clean-cssbak",
     "publish-gh-pages": "docusaurus-publish",
     "write-translations": "docusaurus-write-translations",
     "version": "docusaurus-version",