Created model card for XLM model

[AshAnand34]

What does this PR do?

This pull request updates the XLM model documentation to improve clarity, add usage examples, and enhance the overall presentation. The changes include a new layout for badges, detailed usage examples with code snippets, and reorganized content for better readability as outlined in #36979.

Documentation Enhancements:

• Added a floating badge section for PyTorch and TensorFlow at the top of the page to visually highlight supported frameworks.
• Included detailed usage examples for masked language modeling using both the Pipeline and AutoModel classes, complete with Python code snippets.

Content Reorganization:

• Rewrote and reorganized the "Overview" and "Model Details" sections to improve clarity and readability. Key features and training objectives are now presented in a concise bullet-point format.
• Moved usage tips to a dedicated "Usage Tips" section, emphasizing the importance of selecting the correct checkpoint and using the lang parameter for multilingual tasks.

Additional Features:

• Added a "TIP" section to guide users to explore more examples of XLM applications via the sidebar.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

Who can review?

@stevhliu

[stevhliu]

Thanks! See my comments on your other PRs and apply them to this one as well :)

[stevhliu]

Thanks for your contribution!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.