support lcel (Chainlit#508)

* support lcel

* fix mypy

allow toggle color customisation

add on_message breaking change to changelog

revert action button color change

Config/baseurl (Chainlit#436)

update version and changelog (Chainlit#395)

prevent langchain to be imported by default (Chainlit#350)

Wd/0.6.401 (Chainlit#349)

* fix last message loading

* make follow_symlink default to False and configurable

* relax fastapi version requirement

* fix local db client

* try to stringify content instead of throwing

* remove prints

Update CHANGELOG.md

fix cloud client update message