Generate godoc for pkg with generics

Go 1.18 is here with the addition of the generics. This is like the biggest change to the language since version 1 and consequently it has many impacts to the tooling around the code.

One of these impacts is the godoc command deprecation replaced by the command pkgsite.

When you create your own pkg, and you want to test your godoc locally you have first to build pkgsite

git clone https://go.googlesource.com/pkgsite pkgsite
cd pkgsite
go install ./cmd/pkgsite

with the pkgsite command ready, you can cd in your pkg root directory, where your go.mod file is, and launch the godoc http server

# Go to the root directory of your project
cd your/project/root/directory/
# Execute pkgsite without parameters
~/source/bin/pkgsite
Listening on addr http://localhost:8080

You can finally visualize your documentation. If the URL of your pkg is github.com/gsempe/xxxx, you can see the documentation of your pkg at the address http://localhost:8080/github.com/gsempe/xxxx