Test examples from docs

I tested all of the examples that are shown in the documentation and fix images/code when they were not working

There are two missing things:

• method fade_mask: find the volume to use as example
• in the cli commands like: 'qim3d gui --data-explorer' move the qim3d-icon.svg , we have already create a new task for this

requested review from @fima

assigned to @s212246

added 8 commits

• 97883e79...1a19e375 - 7 commits from branch main
• bbf538ef - Merge branch 'main' into 'test_examples'

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approved this merge request

merged

mentioned in commit a38d5a03