"GitHub repo file count" counts not all files

### Are you experiencing an issue with...

shields.io

### 🐞 Description

Repo [cn007b/stash](https://github.com/cn007b/stash) has many directories and each directory holds many files,
but `GitHub repo file count` from https://shields.io/category/size returns only 4, here: 
which is definitely incorrect, for example only [this directory](https://github.com/cn007b/stash/tree/master/ed/p) has 14 files.

### 🔗 Link to the badge

https://img.shields.io/github/directory-file-count/cn007b/stash

### 💡 Possible Solution

Probably `GitHub repo file count` should iterate over all files over all directories recursively,
it might be expensive in terms of processing time,
probably some sort of caching must be introduced,
but it would be nice to have this insights, IMHO.

Start from the GitHub repo file count badge at https://img.shields.io/github/directory-file-count/cn007b/stash and trace its implementation and GitHub repository data lookup. Compare the result with the linked cn007b/stash directory, including ed/p, and determine how recursive counting and any required caching should be handled; done means the badge reports files across nested directories accurately.

Written by the indexing model from the issue text.