Feature
* feat: add prerelease functionality (413)
* chore: add initial todos
* feat: add prerelease tag option
* feat: add prerelease cli flag
* feat: omit_pattern for previouse and current version getters
* feat: print_version with prerelease bump
* feat: make print_version prerelease ready
* feat: move prerelease determination to get_new_version
* test: improve get_last_version test
* docs: added basic infos about prereleases
* feat: add prerelease flag to version and publish
* feat: remove leftover todos
Co-authored-by: Mario Jäckle <m.jaecklecareerpartner.eu> ([`7064265`](https://github.com/python-semantic-release/python-semantic-release/commit/7064265627a2aba09caa2873d823b594e0e23e77))