"timeshit": Add support for entry comments.

bin/timeshit

@@ -4,11 +4,12 @@ A little tool to parse and summarise basic plain-text timesheets.
 
 Inspired by <https://github.com/dantleech/pttlog>, but much smaller in
 scope. A timesheet file represents a day of tasks, and entries are lines
-that start with a timestamp followed by a description, eg:
+that start with a timestamp followed whitespace and a description, eg:
 
 09:00 Morning routine and meeting
 09:30 A task that lasts an hour
 10:30-12:00 Another task with an optional end time
+13:00 Another task # Everything after the "#" is ignored.
 
 Entries must be in chronological order. If an entry does not include an
 end time the start time of the following task is used, unless it is the
@@ -74,6 +75,8 @@ def main(arguments: argparse.Namespace) -> None:
         except ValueError:
             raise TimesheetParseError("entry has no description", i + 1)
 
+        description = description.split("#")[0].strip()
+
         if "-" in time:
             start, end = time.split("-")
             entries.append(