* feat: add algorithm to evaluate postfix strings
* feat: add test case for evaluate expression
* update: add literature reference
* fix: import name in testcase
* fix: test case result
* Make clear that this is postfix
* Update tests
* add: see reference
* fixes mentioned issues
* Fix `default` case
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Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
