Bump htmltools requirement

setup.cfg

@@ -37,7 +37,7 @@ install_requires =
     starlette>=0.17.1
     websockets>=10.0
     python-multipart
-    htmltools>=0.2.1
+    htmltools>=0.3.0.9000
     click>=8.1.4
     markdown-it-py>=1.1.0
     # This is needed for markdown-it-py. Without it, when loading shiny/ui/_markdown.py,