GIT: How can I add an empty folder to a repository?

Let's start with a tiny bit of background information: Git does not care about folders - it cares about files. Therefore, if a folder is empty, Git will not offer you to add it to version control.

While there is no "standard" solution to this problem, there are a couple of different approaches to "circumvent" this behavior.

Adding a .keep File

A popular solution is to simply add a file named ".keep" in the corresponding folder. You can now stage and commit this file and, as a consequence, also add the folder to version control.

Note that .keep is not a "magical" name but rather a popular convention. Also, the file doesn't serve any other purpose beyond making its containing folder visible to Git.