Documentation: Add documentation for different use cases and examples

[junwen-k]

A good open source library cannot go without a good documentation!

Suggest to add in documentation for different use cases and examples.
A good starting point could be based on the existing features:

1. Text
2. Image
3. Table
4. Shape
5. Canvas
6. Group

Maybe it can also be linked back to Microsoft OpenXML's documentation for easier references.

Easier way to get started is by directly writing into the repository's README file but it could get cluttered real quick.

Perhaps having a Nextra documentation site would be helpful.
https://nextra.site/docs/docs-theme/start

[fumiama]

That's a good idea and we can use github wiki as the extra documentation site. I'll be going on it as soon as I'm free. Anyone who is interested in this project can also help us to improve the documentation by PR or opening issues.

[lordofscripts]

I agree that documentation is required, otherwise what's the use of it?