Support reading multi-line input in `Ronin::Core::CLI::Shell.start`

[postmodern]

Support reading multi-line input using Reline.readmultiline(prompt, use_history) { |multiline_input| ... } with a block that checks if the last line is the closing line. We will need to count opening/closing quotes to determine if the input has been "closed". Example: https://github.com/ruby/reline#multi-line-editing-mode

[postmodern]

This would require detecting when the multi-line input begins and ends, which would vary based on the command or the type of shell.