* docs: Fix typos and minor improvements
* feat: Log the backup stats summary to a CSV file
The log records the added, removed and snapshot size after each backup.
* feat: Add the snapshot ID to the stats log
* docs: Update README with the stats log info
* fix: Linter 1: Quote var
* fix: Linter 2: Shellcheck declare and assign separately
* feat: Turn the stats log into an opt-in