Update scikit image to 0.18 (#435)

* update scikit-image

* update docs poetry lock

* update changelog

Author: daniel-wer

docs/poetry.lock

@@ -12,7 +12,8 @@ For upgrade instructions, please check the respective *Breaking Changes* section
 ### Breaking Changes
 ### Added
 ### Changed
- - The `Vec3Int` constructor now asserts that its components are whole numbers also in numpy case. [#434](https://github.com/scalableminds/webknossos-libs/pull/434)
+- The `Vec3Int` constructor now asserts that its components are whole numbers also in numpy case. [#434](https://github.com/scalableminds/webknossos-libs/pull/434)
+- Updated scikit-image dependency to 0.18.3. [#435](https://github.com/scalableminds/webknossos-libs/pull/435)
 ### Fixed
 
 ## [0.8.16](https://github.com/scalableminds/webknossos-cuber/releases/tag/v0.8.16) - 2021-09-22