Build and publish a .exe file as a release asset for windows users

[gldraphael]

This will make it possible to install viu using a package manager like scoop so that users dont need rust installed.

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Until this is addressed, Windows users can build viu and run it locally:

# Install rust
scoop install rust

# add cargo bin path to PATH
$env:Path += ";$HOME\.cargo\bin"

# Build & Install
git clone https://github.com/atanunq/viu.git
cd viu\
cargo install --path .

# you should be golden now... try one of the files in the img folder
viu .\img\gifdemo.gif