debchange: Add --date argument for specifying the changelog entry date
This commit introduces the --date argument to the debchange command, allowing users to specify a specific date in RFC 5322 format for the changelog entry being edited.
Example usage: $ debchange -i --date "Tue, 23 Jun 2023 12:34:56 +0530"
Signed-off-by: Vignesh Raman vignesh.raman@collabora.com