Feature request: Add support for additional support files

[VorpalBlade]

It would be useful to have support for additional support files.

For example:

• Shell completion files (bash, zsh)
• Man pages
• Dynamic libraries
• Support binaries (I need a separate binary to work as a LSP language server that goes along with my program with an embedded scripting language, Rune unfortunately doesn't currently support having both in a single binary)

Since this is a very general problem (and it wouldn't be clear where to put the specific files), perhaps a generic callback that the application author could implement would be a way to do this. For example:

self_update::backends::github::Update::configure()
    .repo_owner("...")
    .repo_name("...")
    // ...
    .handle_additional_files(|archive_iterator| { /* ...*/ }
    .update();