document ignore capability in pijul add

Dependencies

• [2] TZVUNELW Documentation comments
• [*] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).

Change contents

• edit in pijul/src/main.rs at line 77
  [2.180]

  [4.85269]
  + ///

  + /// Users can ignore files and directories by placing the relevant paths

  + /// in one or more `.ignore` files using git's pattern syntax.