Revampt as dotnet-cat

[kzu]

Given https://www.linfo.org/cat.html definition:

cat is one of the most frequently used commands on Unix-like operating systems. It has three related functions with regard to text files: displaying them, combining copies of them and creating new ones.

And the catbag concept, we want to:

• Rename project to dotnet-cat
• Revamp implementation to use Spectre.Console for better progress and overall output
• Leverage proper globing for more precise sync
• Add significant test coverage to improve reliability since the globing isn't trivial

Some key features:

• Should allow flexible globing with multiple include/exclude strings, such as:

[file]
  url = https://github.com/git-ecosystem/git-credential-manager/tree/v2.6.0/src/shared/Core/Interop
  include = *.cs
  include = **/*FileSystem.cs
  exclude = **/MacOS/**/*.*

• CLI should allow specifying this via multiple -i|--include and -e|--exclude options.
• CLI should provide a --dry-run for all commands (including add, so you can test your include/excludes)
• Include/exclude would only be supported initially for github tree URLs (since it requires the GH CLI to fetch the directory contents)