feat: ✨ use correct system icons + update icon documentation in general

[mariohamann]

Issue to be solved

The package storybook-addon-fetch-mock messed up data:-requests, which made it impossible to use it anymore. After digging in the source code and issues of the package (https://github.com/JohnAlbin/storybook-addon-fetch-mock) and its dependency (https://github.com/wheresrhys/fetch-mock) I found a PR, that would fix it: wheresrhys/fetch-mock#607 – but I even it could get it work.

On top: Both packages aren't up-to-date and don't get any updates. I therefore decided to remove them and write the mock function myself. In the end we save a ton of JS in Storybook's frontend, everything feels more maintainable + it just works™️.

Summary of the PR

1. Fix of the fetch bug
2. Updated the system icons that it reflects only the icons we currently need. (In preperation for feat(dev): add sd-accordion/-group component #11)
3. Removed the default library, as this links to bootstrap icons we don't integrate and there we don't need the resolver.
4. Added story for system icons, to give an overview of the integrated icons + test them proberly
5. Renamed the current library stories to make clear, that they are examples and not integrated in the components.

[mariohamann]

@solid-design-system/development