docs: add example assets button

[SMoraisAnsys]

Description

Adding a button to download the examples assets. I had too add a work around to ensure that the 3 download buttons were aligned somehow "correctly". See the result below

If that's fine with you, we can leave it like that for the moment as we have to test that assets are correctly uploaded and available for download through the documentation. A next step (PR) could be to remove the buttons and only use text content with hyperlinks to trigger the downloading of files.

Issue linked

Related to #497
Close #517

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have assigned this PR to myself.
• I have made sure that the title of my PR follows Conventional commits style (e.g. feat: add optical property)
• I have agreed with the Contributor License Agreement (CLA).

[StefanThoene]

@SMoraisAnsys i renamed the path in all examples to assets_data_path so its more clear
can be merged from my perspective