Support passing exact next version and additional release notes

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There are situations, when badabump bumps project to lower version than needed: for example when there is one commit of,

• build: Update to Python 3.10

badabump will bump 21.2.3 version to 21.2.4, but in reality it is needed to be bump to 21.3.0.

Need to define a way to pass an exact next version on invoking badabump, so it will make all the CHANGELOG changes and stuff, but for requested version, not for auto-generated.

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Another nice feature to have is expecting on additional release notes to be passed to badabump. Using example above it would be nice to have a way to pass Ensure Python 3.10 support. line, which should be included to CHANGELOG.