PyPSA/linopy: v0.2.3

What's Changed Missing + sign in objective function by @aurelije in https://github.com/PyPSA/linopy/pull/146 A PyPSA-based problem is not necessary linear. by @LucieRC in https://github.com/PyPSA/linopy/pull/148 .cumsum for Variables and LinearExpression by @hblunck in https://github.com/PyPSA/linopy/pull/147 expression: fix constant-constant multiplication by @FabianHofmann in https://github.com/PyPSA/linopy/pull/151 New Contributors @aurelije made their first contribution in https://github.com/PyPSA/linopy/pull/146 @LucieRC made their first contribution in https://github.com/PyPSA/linopy/pull/148 @hblunck made their first contribution in https://github.com/PyPSA/linopy/pull/147 Full Changelog: https://github.com/PyPSA/linopy/compare/v0.2.2...v0.2.