feat(readme.md): adds `emerge` package in GURU

[Ahwxorg]

Title says it all.

root # emerge -s glow

returns

*  app-misc/glow
      Latest version available: 1.5.1
      Latest version installed: 1.5.1
      Size of files: 172855 KiB
      Homepage:      https://github.com/charmbracelet/glow
      Description:   Render markdown on the CLI, with pizzazz!
      License:       Apache-2.0 BSD-2 BSD MIT MPL-2.0

[Ahwxorg]

More about GURU is available here.