doc: add default/overridable settings in env file base

etc/env

@@ -20,3 +20,22 @@ export MATRIX_HOOK_ROOMID=
 # Specify these two if oom-killer is getting nasty with things
 export TMPDIR=
 export GOGC=1
+
+# The following settings all have a default in the backup.sh itself, but you can override them here
+#BACKUP_PATHS="/"
+#BACKUP_EXCLUDES="/etc/restic/exclude"
+#
+#BACKUP_TAG=$(hostname -s)
+#
+#
+#RETENTION_DAYS=7
+#RETENTION_WEEKS=4
+#RETENTION_MONTHS=3
+#RETENTION_YEARS=1
+#
+#CURL="/usr/bin/curl"
+#FIND="/usr/bin/find"
+#RESTIC="/usr/bin/restic"
+#ECHO="/usr/bin/echo"
+#
+#HOST=$(hostname -s)