Docs: Improve readability of values for flags in markdown

[tordans]

I want to propose to roll out the change showecased in this PR to the whole readme.

My issue is, that I find the current formatting where the example value is italic but not part of the <code> tag very hard to read.

I propose to use some other way to signal that som strings are placeholder text and wrap the whole segment as a code block.

Before

After

After:

I picked <example_value>, but other wrappers would be possible to, of course.

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I did not do this for the whole readme, yet, in order to first get feedback if this PR would be welcome.