Add dl.filippo.io instructions to the README

Fixes #367

README.md

@@ -77,6 +77,12 @@ go build -ldflags "-X main.Version=$(git describe --tags)"
 
 or use [the pre-built binaries](https://github.com/FiloSottile/mkcert/releases).
 
+```
+curl -JLO "https://dl.filippo.io/mkcert/latest?for=linux/amd64"
+chmod +x mkcert-v*-linux-amd64
+sudo cp mkcert-v*-linux-amd64 /usr/local/bin/mkcert
+```
+
 For Arch Linux users, [`mkcert`](https://www.archlinux.org/packages/community/x86_64/mkcert/) is available on the official Arch Linux repository.
 
 ```