Add instructions

README.md

+To develop locally with MongoDB, it is useful to have a database with a web
+user interface to play around and see what your code does. This is especially
+useful to *test* the code of future unit tests.
+
+RUn
+
+```console
+docker run -d --net host mongo
+docker run -d --net host mrvautin/adminmongo
+```
+
+Open [localhost:1234](http://localhost:1234) and enter `mongodb://localhost/`.