Add cram test for the examples

[Willenbrink]

Previously, the examples were there but not tested and IIUC not even compiled during publishing/testing. This leads to them bitrotting. This PR adds simple cram tests that start the server from the respective example and test the output via curl.

I've only implemented the tests for the first few examples as some examples don't compile currently or require more advanced curl knowledge.

There are a few issues documented in the README.md such as:

• The curl command might be run before the server becomes available
• The tests all use the same port so they cannot be run concurrently
• The logs contain timestamps which prevents reproducible tests using them

I don't think these are large issues and can be addressed in a later PR.

[Willenbrink]

We should maybe wait with that change until after the next release