Minor fixes of documentation and prompt

[zechengz]

Description

Minor fixes to

1. .gitignore
2. Documentation in some files
3. Add required overriding class to BaseToolAgent
4. Minor fix of camel/prompts/code.py
5. Minor fix of requirements.txt

Motivation and Context

Better user experience etc.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of example)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.

[lightaime]

Thanks, @zechengz! LGTM.