feat: add command line interface and the option to specify a custom config file

[flexiondotorg]

Description

This patch adds the essential command line options, --help, --version and --config. It also fixes a bug where the config file would always default to the one in the current directory.

• Resolves feat: Add option to specify config file location on the command line #20

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation (updates the documentation)

Checklist:

• I have performed a self-review of my code
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections
• I have made corresponding changes to the documentation