Update dropdown chapter of CONTRIBUTING.md based on practical feedback (#360)

* improve dropdown paragraph based on Seo's feedback

* add one sentence and improve wording

* add changelog

---------

Co-authored-by: Luis <ge34lah@mytum.de>

Author: LuisHeinzlmeier

CONTRIBUTING.md

@@ -157,7 +157,11 @@ The first sentence of key takeaway 2.
 If you want to link a key takeaway to a certain heading in your chapter, add `<section-name>-<notebook-name>-key-takeaway-<key-takeaway-number>` as a label before the heading.
 Replace all `_` with `-`, and the card of the key takeaway will be linked to the heading in the text (e.g., `(preprocessing-visualization-dimensionality-reduction-key-takeaway-2)=`).
 
-You can insert the dropdowns locally by calling `make dropdown` before `make`.
+Our CI workflow (`.github/worksflows/build_book.yml`) will call `make dropdown` when building the book.
+For testing, you can insert the dropdowns locally by calling `make dropdown` before `make`.
+
+> [!WARNING]
+> Executing `make dropdown` locally will modify nearly all notebook files. These changes should never be committed or pushed to the repository. We recommend discarding these changes immediately after running the command using `git restore .`. Ensure you’ve staged your wanted changes (`git add`) beforehand.
 
 ## Data access
 

changelog.d/360.added.md

@@ -0,0 +1 @@
+Update dropdown chapter of `CONTRIBUTING.md` based on practical feedback ([#360](https://github.com/theislab/single-cell-best-practices/pull/360)) <sub>@LuisHeinzlmeier</sub>