Pkg.clone no longer exists.

[NAThompson]

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.0-DEV.883 (2021-11-03)
 _/ |\__'_|_|_|\__'_|  |  Commit b1cf46ce69 (8 days old master)
|__/                   |
julia> using Pkg

julia> Pkg.clone("https://github.com/m-j-w/TerminalGraphics.jl")
ERROR: UndefVarError: clone not defined
Stacktrace:
 [1] getproperty(x::Module, f::Symbol)
   @ Base ./Base.jl:31
 [2] top-level scope
   @ REPL[8]:1

The instructions in the README.md therefore fail.