Merge: Rework Mixture Examples (#394)

- added example for traditional mixture
- reworked example for slot-based mixtures
- grouped both mixture examples under a new example category `Mixtures`

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Added
 - `allow_missing` and `allow_extra` keyword arguments to `Objective.transform`
+- Example for a traditional mixture
+
+### Changed
+- Example for slot-based mixtures has been revised and grouped together with the new 
+  traditional mixture example
 
 ### Deprecations
 - Passing a dataframe via the `data` argument to `Objective.transform` is no longer

docs/userguide/constraints.md

@@ -197,7 +197,7 @@ Without this constraint, combinations like below would be possible:
 | 3 | Octanol   | Octanol   | would be excluded                        |
 
 The usage of `DiscreteNoLabelDuplicatesConstraint` is part of the
-[example on mixtures](../../examples/Constraints_Discrete/mixture_constraints).
+[example on slot-based mixtures](../../examples/Mixtures/slot_based).
 
 ### DiscreteLinkedParametersConstraint
 The [`DiscreteLinkedParametersConstraint`](baybe.constraints.discrete.DiscreteLinkedParametersConstraint)
@@ -367,7 +367,7 @@ DiscretePermutationInvarianceConstraint(
 ```
 
 The usage of `DiscretePermutationInvarianceConstraint` is also part of the
-[example on mixtures](../../examples/Constraints_Discrete/mixture_constraints).
+[example on slot-based mixtures](../../examples/Mixtures/slot_based).
 
 ### DiscreteCustomConstraint
 With a [`DiscreteCustomConstraint`](baybe.constraints.discrete.DiscreteCustomConstraint) 

examples/Mixtures/Mixtures_Header.md

@@ -0,0 +1,4 @@
+# Mixtures
+
+These examples demonstrate how to set up mixture use cases in the traditional as well
+as in the slot-based representation.