[IMP] account_cancel: Update manifest description

Added more detailed description of what the module does.

addons/account_cancel/__manifest__.py

@@ -9,9 +9,18 @@
 Allows canceling accounting entries.
 ====================================
 
-This module adds 'Allow Canceling Entries' field on form view of account journal.
-If set to true it allows user to cancel entries & invoices.
-    """,
+This module adds a checkbox on the accounting journals to allow the cancellation of journal entries.
+
+This checkbox is only visible on the accounting journals when the debug mode is active.
+
+If this checkbox is set to TRUE, it allows users to cancel journal entries.
+
+The accounting entry that is cancelled can then be modified and reposted or deleted.
+
+It also operates on invoices, bank statements, payments ...
+
+Be careful with this module as it has audit implications. Cancelling accounting entries is not authorized in all countries.
+""",
     'website': 'https://www.odoo.com/page/accounting',
     'depends': ['account'],
     'data': ['views/account_views.xml'],