Add example-shttp-fileserver

[matzf]

Add example for simple fileserver that lists/serves all files under the current working directory.

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This change is 

[juagargi]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[cmeury]

I would have proposed two additions:

• Output requests and errors
• Provide the option to cache files in memory

[matzf]

@cmeury #157