Add header and footer for yaml linting. Add additional spaces before …

…comments.

config.yaml.example

@@ -1,9 +1,9 @@
 # Copy this file to config.yaml to use.
-
+---
 calendars:
   # Change 'Calendar 1' to the name of the calendar to read
   Calendar 1:
-    tabs: [ # List all tabs that should be linked to the calendar.
+    tabs: [  # List all tabs that should be linked to the calendar.
       'Sheet Tab 1',
     ]
 
@@ -13,12 +13,13 @@ spreadsheet:
   tabs:
     # Change 'Sheet Tab 1' to the name of the spreadsheet sheet/tab
     Sheet Tab 1:
-      aliases: [ # Add aliases as necessary, one per line.
+      aliases: [  # Add aliases as necessary, one per line.
         'alias 1',
         'alias 2',
       ]
-      start: # Don't change 'start'.
-        cell: B3 # First top-left cell in the sheet.
+      start:  # Don't change 'start'.
+        cell: B3  # First top-left cell in the sheet.
         # Both year and month determine the row offset.
         year: 2019
         month: 9
+...