doc: How to enable csml bots in self hosted

add documentation to enable csml bots

ref: https://discord.com/channels/647412545203994635/650257251856285707/1107141091314114560
https://discord.com/channels/647412545203994635/1084554168129306715/1084729801274818620


required env variable
```
CSML_BOT_HOST
CSML_BOT_API_KEY
CSML_EDITOR_HOST=https://csml-editor.cdn.chatwoot.com
```