code comment

[meua]

Dear developer,

Many developers who are new to dora noticed that dora-rs code is lacking in documentation and comments. Comments are an essential part of code as they improve its readability and maintainability. The absence of comments can make it difficult for other developers to understand the intent and implementation of dora-rs code, and can pose unnecessary difficulties for the long-term maintenance of the project.

Therefore, I recommend adding sufficient comments and documentation to dora-rscode to make it easier for other developers to understand and use. Here are some suggestions:

• Add comments before each function and method to explain their purpose, input/output parameters, and data types.

• Add necessary comments in the code to explain key algorithmic ideas and implementations.

• Add comments before classes and modules to explain their functionality and purpose.

• Add comments in critical parts of the code, such as exception handling, loops, and conditional statements.

• Add comments in the code to explain its relationship and dependencies with other code.

I hope these suggestions will be helpful in making dora-rs more understandable and maintainable. Thank you!

[meua]

There are many students learning dora-rs now, but they say that the dora-rs code lacks a lot of field descriptions, causing beginners to not know the meaning of these fields.
For example：

[heyong4725]

@phil-opp @haixuanTao I totally agree with this suggestion. Accessibility is one of the most important factor for open source adoption. So I would suggest that now it might be a good time to review all the stable code base and add comments, as Dora is being introduced to lots of students.

[haixuanTao]

I have opened a PR to address this very example: #321