Addressing #1395 but with a different solution from #1478, using
semantic versioning based on implementation found
[here](https://distresssignal.org/busting-css-cache-with-jekyll-md5-hash).
Implemented a way of calculating the hash for both a single file or
directory. This way we can calculate the hash for when there is a change
in the `_sass` dir, for example, or in the contents of a single file.
Examples of generated outputs of the plugin:
```
/al-folio/assets/css/main.css?d41d8cd98f00b204e9800998ecf8427e
/al-folio/assets/js/theme.js?96d6b3e1c3604aca8b6134c7afdd5db6
/al-folio/assets/js/dark_mode.js?9b17307bb950ffa2e34be0227f53558f
/al-folio/assets/js/no_defer.js?d633890033921b33e0ceb13d22340a9c
/al-folio/assets/js/common.js?acdb9690d7641b2f8d40529018c71a01
/al-folio/assets/js/copy_code.js?c9d9dd48933de3831b3ee5ec9c209cac
/al-folio/assets/img/prof_pic.jpg?974957d202f671e4fa6700c04e68deae
```
Signed-off-by: George Araujo <george.gcac@gmail.com>
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