mkcert is not amd64 only

[AndreiCherniaev]

Bad advice is detected in readme https://github.com/FiloSottile/mkcert/blob/1c1dc4ed27ed5936046b6398d39cab4d657a2d8e/README.md?plain=1#L81

We should avoid hard-coded to architecture. Don't say this is just example. Even smart Canonical peoples copy-past it.

I see two options to fix:

1. Make if-then script based on dpkg --print-architecture output or similar relative to OS
2. The best idea is to use well-known tools to download from github, for example, binup. Examples how to use binup

sudo ./binup install --project mxmlnkn/rapidgzip --path '/usr/bin'
./binup -v install --project FiloSottile/mkcert

But mkcert should be packed in archive!

So regardless to architecture, I suggest to put mkcert release in tar.gz. In this case we can avoid chmod +x /usr/local/bin/mkcert and use binup. Github release in archive is de-facto standard, most of popular software use this way (example1, example2).