Mention that dropdowns depend on popper.js too.

docs/4.0/getting-started/javascript.md

@@ -14,7 +14,7 @@ Plugins can be included individually (using Bootstrap's individual `*.js` files)
 
 Some plugins and CSS components depend on other plugins. If you include plugins individually, make sure to check for these dependencies in the docs. Also note that **all plugins depend on jQuery** (this means jQuery must be included **before** the plugin files). [Consult our `package.json`]({{ site.repo }}/blob/v{{ site.current_version }}/package.json) to see which versions of jQuery are supported.
 
-Our tooltips and popovers also depend on [Popper.js](https://popper.js.org/).
+Our dropdowns, popovers and tooltips also depend on [Popper.js](https://popper.js.org/).
 
 ## Data attributes