Update dotenv support to make operative (#564)

b46ada9f72 added support for dotenv files to be loaded in lieu of
actual environment variables. This code has since been neglected across
infrastructure changes that removed the need for an env file, moved
its location, and changed dependency management style.

This won't be operative in production (and already isn't, since there'd
be an ImportError on 'dotenv' if so) but makes some local testing
setups more convenient.

.gitignore

@@ -1,6 +1,4 @@
-image.*
-video.mp4
-video.webm
+# Python, Flask, IDEs
 cache/
 __pycache__/
 .idea/
@@ -12,3 +10,11 @@ flask_session/
 .DS_Store
 .venv
 *.pyc
+
+# rdrama Media Runtime Artifacts
+image.*
+video.mp4
+video.webm
+
+# Optional env file for some environments
+env