add that 1 shift is 8h

fsoubelet · fsoubelet · commit 8152add1dbb8 · 2025-12-17T14:38:24.000+01:00
diff --git a/docs/logbook/admonition_shifts b/docs/logbook/admonition_shifts
@@ -7,4 +7,5 @@
     - H = Holidays or weekend (Day)
     - HN = Holidays or weekend (Night)
 
+    A shift consists of an 8h period.
     Hovering the column name will show a tooltip with more information.
