[docs] Update the readme file

[forfudan]

This pull request includes several updates to the README.md file for the DeciMojo library. The changes focus on improving clarity, updating examples, and correcting some inaccuracies in the documentation.

Documentation improvements:

• Revised the overview section to enhance clarity and readability.
• Updated the installation instructions to streamline the process and improve formatting.

Example corrections:

• Corrected the division and mathematical function results in the examples.
• Corrected the example for checking if a decimal is an integer.