Support configuration file for default options

[MatthewMckee4]

Summary

Support a .kountrc or kount.toml configuration file for setting default options, so users don't have to repeat common flags every time. The config file should be searched in the current directory and parent directories.

Example

# .kountrc (or kount.toml)
ext = ["rs", "py"]
sort = "name"
no-ignore = false

# Uses defaults from config file
kount .

# CLI flags override config file
kount --sort lines .

Acceptance criteria

• Reads config from .kountrc or kount.toml in current/parent directories
• CLI flags take precedence over config file values
• Supports all applicable CLI options
• Ignores missing config file silently