Add Support for Multiple Source Directories and SFDX Project Integration

Overview

Introduces support for reading source files from multiple directories or the sfdx-project.json file.

New Features

1. **The --sourceDir flag can now be an array of directories.

2. SFDX Project Integration (--useSfdxProjectJson)

• Automatic directory detection from sfdx-project.json configuration
• Reads all packageDirectories defined in the project configuration
• Supports custom project paths with --sfdxProjectPath

# Automatically read directories from sfdx-project.json
apexdocs markdown --useSfdxProjectJson --targetDir ./docs

# Use sfdx-project.json from a different location
apexdocs markdown --useSfdxProjectJson --sfdxProjectPath ./my-project --targetDir ./docs