Merge pull request 'Load from env var here too' (#1) from decentral1se/lumbung-calendar-prototype:env-var-config into master

Reviewed-on: https://git.vvvvvvaria.org/rra/lumbung-calendar-prototype/pulls/1

event_feed_config.py

@@ -1,6 +1,8 @@
+import os
+
 # a publicly accessible ICS calendar
-calendar_url= ''
+calendar_url = os.environ.get('CALENDAR_URL', '')
 
 # your Hugo content directory
-output_dir = ''
+output_dir = os.environ.get('OUTPUT_DIR', '')