feat(config): more descriptive example config

[Teufelchen1]

Hi 👋

While messing around, I noticed that the example config tries to css_select stuff that is not present on the example website. To be precise: https://edjopato.de/post/ no longer has an article class. This resulted in the following error: ERROR: https://edjopato.de/post/ css_selector (article) selected nothing Further, the regex example seemed also outdated.

This PR aims to fix both issues:

• article is replaced with .content

• The regex now replaces a date in iso format with the string ISO8601

  As well as adding the following feature:

• The example configuration now describes what the example does.

Additionally a refactoring of the code base was attempted:

• The two example-config header were merged into one. This makes the header a bit less fitting for each use case (init <-> print example) but the code base is simplified. I believe this to be a fair trade off, your opinion might differ - say so!
• The config header was moved to a const variable
• The config header location was changed from inline in main.rs to the top of config.rs

There is a test for the ISO8601 regex in this PR - I think it should be removed before merge as it does not test behaviour of the website-stalker. I left it in for this / the first review only.

[Teufelchen1]

First of all:

🌶️

As the example config gets bigger [..] write an src/example-config.yaml file exactly as the total result should be

Good idea.

and include it with include_str!("example-config.yaml")

TIL: include_str!, Thanks!

The example can then be verified with a test like its currently being done already so its still ensured to be working.

There were a lot of ways to do that - at the moment, only one test build the example as before. This could be outsourced to an helper function? Not sure, trying to KISS.

Maybe also name it website-stalker.yaml and place it in the root folder while adding the sites folder to the .gitignore. Then local testing can just be cargo run -- run --all too.

That's the way to go! Please note that any change to the config results in a rebuild now. This is a bit annoying but okay for me.