*Optional.* Bump the version number semantically. The value must
be one of:

  * `major`: Bump the major version number, e.g. `1.0.0` -> `2.0.0`.
  * `minor`: Bump the minor version number, e.g. `0.1.0` -> `0.2.0`.
  * `patch`: Bump the patch version number, e.g. `0.0.1` -> `0.0.2`.
  * `final`: Promote the version to a final version, e.g. `1.0.0-rc.1` -> `1.0.0`.