Add Support for Multiple Paths

[jack45j]

Summary

This PR introduces support for specifying multiple paths as input to the RIBsTreeMaker tool.

Motivation

In certain scenarios, such as when using Bazel or other modular architecture solutions, RIB modules can be independent and not necessarily located within the main project directory. These independent RIB modules may also contain their own sub-RIBs. Hence, supporting multiple input paths is beneficial and necessary to correctly analyze and visualize the entire RIB hierarchy.

Changes

1. Modified the implementation to handle multiple input paths. Specifically, the code:

let paths = allSwiftSourcePaths(directoryPath: firstArgument)

has been changed to:

let paths = firstArgument.split(separator: ",").flatMap { allSwiftSourcePaths(directoryPath: String($0)) }

2. Modified the README to reflect the new usage pattern.