docs: add licensing reference in README.md file

Adding a reference to the LICENSE.md file in the main readme file for
this project. This is to clarify what kind of licensing is this
repository released under.

README.md

@@ -29,3 +29,6 @@ When building the same docker images multiple times, it is easy to leave a lot o
 without tags, especially when using `<latest>` tags. These eat up precious space in the
 hard drive and have little benefit. The convenience script executes the `docker rmi` command for all
 images with no tags assigned.
+
+## License
+The contents of this repository are covered under the [MIT License](LICENSE.md)