chore: add .env.example, ignore real env files, update README setup (#3147)

Co-authored-by: Wendong-Fan <133094783+Wendong-Fan@users.noreply.github.com>

Author: coolbeevip

.env renamed to .env.example

@@ -432,8 +432,9 @@ benchmark/gaia/results.jsonl
 # Secret files for docker
 .container/.env
 
-# Environment variables file
-.env
+# Environment variables files (ignore real envs, keep examples)
+/.env*
+!/.env*.example
 
 ##### Node.js/TypeScript.gitignore #####
 # Hybrid Browser Toolkit TypeScript
@@ -462,4 +463,4 @@ yarn-error.log*
 *.tgz
 
 # Yarn Integrity file
-.yarn-integrity
+.yarn-integrity

.gitignore

@@ -246,6 +246,13 @@ This example demonstrates how to create a `ChatAgent` using the CAMEL framework
   export OPENAI_API_KEY='your_openai_api_key'
   ```
 
+   Alternatively, use a `.env` file:
+
+   ```bash
+   cp .env.example .env
+   # then edit .env and add your keys
+   ```
+
 3. **Run the following Python code:**
 
   ```python
@@ -608,4 +615,4 @@ The source code is licensed under Apache 2.0.
 [reddit-url]: https://www.reddit.com/r/CamelAI/
 [reddit-image]: https://img.shields.io/reddit/subreddit-subscribers/CamelAI?style=plastic&logo=reddit&label=r%2FCAMEL&labelColor=white
 [ambassador-url]: https://www.camel-ai.org/community
-[package-download-url]: https://pypi.org/project/camel-ai
+[package-download-url]: https://pypi.org/project/camel-ai