[skip ci] Update changelog and some cosmetic changes to CONTRIBUTING.md

Author: mdbenito

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## Unreleased - 💥 More breaking changes and new algorithms 🏭 
+## 0.4.0 - 🏭💥 New algorithms and more breaking changes
 
 - GH action to mark issues as stale
   [PR #201](https://github.com/appliedAI-Initiative/pyDVL/pull/201)
@@ -31,10 +31,8 @@
   [PR #240](https://github.com/appliedAI-Initiative/pyDVL/pull/240)
 - Fixes bug in ray initialization in `RayParallelBackend` class
   [PR #239](https://github.com/appliedAI-Initiative/pyDVL/pull/239)
-- Improves Least Core methods by solving an egalitarian quadratic program
-  to find a fair distribution of data value that satisfies the constraints
-  given the least core value found by solving the least core linear program,
-  adds cvxpy as a dependency and uses it instead of scipy to solve these programs.
+- Implements "Egalitarian Least Core", adds [cvxpy](https://www.cvxpy.org/) as a
+  dependency and uses it instead of scipy as optimizer
   [PR #243](https://github.com/appliedAI-Initiative/pyDVL/pull/243)
 
 ## 0.3.0 - 💥 Breaking changes

CONTRIBUTING.md

@@ -263,12 +263,10 @@ runs](#skipping-ci-runs)).
 
 ### Skipping CI runs
 
-You sometimes would like to skip CI for certain commits (e.g. updating the readme). 
-In order to do that you can simply prefix the commit message with `[skip ci]`.
-
-- Other strings, like `[ci skip]` are allowed, but we prefer `[skip ci]`.
-- The string doesn't have to be at the beginning of the commit message, but we prefer doing it 
-  that way because it makes it immediately apparent when looking at commits in a PR.
+One sometimes would like to skip CI for certain commits (e.g. updating the
+readme). In order to do this, simply prefix the commit message with `[skip ci]`.
+The string can be anywhere, but adding it to the beginning of the commit message
+makes it more evident when looking at commits in a PR.
 
 Refer to the official [GitHub documentation](https://docs.github.com/en/actions/managing-workflow-runs/skipping-workflow-runs) 
 for more information.
@@ -290,13 +288,13 @@ Then, a new release can be created using the script
 part):
 
 ```shell script
-./scripts/release-version.sh 0.1.6
+build_scripts/release-version.sh 0.1.6
 ```
 
 To find out how to use the script, pass the `-h` or `--help` flags:
 
 ```shell script
-./build_scripts/release-version.sh --help
+build_scripts/release-version.sh --help
 ```
 
 If running in interactive mode (without `-y|--yes`), the script will output a