Deprecate dead project

[hickford]

Is this project dead? I see no commits since September 2021. Consider deprecating and linking to fork https://github.com/cli/browser which is actively developed.

https://go.dev/ref/mod#go-mod-file-module

To deprecate a module, an author may add a // Deprecated: comment and tag a new release. The author may change or remove the deprecation message in a higher release.