insert-rfc5322-date: Inserts an RFC5322 date at the cursor

In my work, I often need to insert a date/time that comforms to the RFC 5322 format at the current editing position in Visual Studio Code. Although I can obtain such a date by running the command date -R on my Ubuntu machine, I still want to make it a bit easier with a couple mouse clicks. Hence the birth of this VS Code extension.