[docs] add/update choco, scoop, winget instructions

[dpprdan]

This adds/updates Windows installation instructions with chocolatey, scoop, and winget.

The scoop and choco manifests do not include the git and gpg4win dependencies, so they have to be installed separately. Should we add those to the README?
There is a choco install gpg4win there already, which is why I added winget install git and winget install gpg4win. The alternative would be to add the dependencies to the manifests so that choco/scoop install gopass would also install the dependencies.

The winget manifest already includes both dependencies, but the winget cli does not support installing those just yet (the next minor version will add this functionality). winget probably needs some more time to properly support dependencies (i.e. I am currently failing at submitting the manifest with dependencies included due to (IMHO) overzealous checks).

BTW is this warning still valid?

gopass/docs/setup.md

Line 204 in 439bc00

**WARNING**: Windows is not yet officially supported. We try to support it in the future. These are steps are only meant to help you setup gopass on Windows so you can provide us with feedback about the current state of our Windows support.

[AnomalRoil]

You're right, I think the warning can go, Windows support is there to stay.

[dpprdan]

I still wonder what the best strategy re the dependencies/backends is (on Windows). gopass installs fine without them and you can also run it without them. age is also an alternative to gpg, but I don't know how well it works in Windows. So I see three options:

1. do not add dependencies to the manifests, and
   a. just add git and gpg4win them to the installation instructions.
   b. add git, gpg, and, alternatively age (not sure whether it is in any of the package manager repos, though) to the installation instructions.
2. add git and gpg4win to the manifests so they get automatically installed with gopass (where possible, otherwise 1a - I assume that this should work with choco and scoop)

[dominikschulz]

Thanks!