📝 Add a docs section about runtime requiements

docs/getting-started.rst

@@ -6,3 +6,26 @@ The documentation isn't ready yet so I suggest you going through the
 understanding of GitHub Apps and how to write them with octomachinery.
 
 .. _`How-to create a GitHub Bot tutorial`: https://tutorial.octomachinery.dev
+
+Runtime pre-requisites
+----------------------
+
+* Python 3.7+ as octomachinery relies on :py:mod:`contextvars` which
+  doesn't have a backport.
+* GitHub App credentials and GitHub Action events are supplied via
+  environment variables. They are also loaded from a ``.env`` file if it
+  exists in a development environment.
+
+  .. warning::
+
+     Be aware that some tools in your environment may conflict with
+     autoloading vars from a ``.env`` file. It is recommended to disable
+     those. One example of such tool is `Pipenv`_.
+
+     .. _`Pipenv`:
+        https://pipenv.readthedocs.io/en/latest/advanced/
+        #automatic-loading-of-env
+
+  For the production deployments, please use a way of supplying env vars
+  via tools provided by the application orchestration software of your
+  choice.