feat(theme): add sway bar color integration

[him-cyber]

Summary

This PR introduces optional integration with the user's Sway configuration to automatically apply bar colors (background and foreground) from the ~/.config/sway/config file. Fix for the open issue #2145

Motivation

As a Wayland-native window manager, Sway allows defining custom bar colors. This enhancement bridges the theme configuration in i3status-rust with Sway’s color settings, improving visual consistency and user experience for Sway users.

Implementation

• Introduced a sway_integration section in config.toml
• Parsed Sway bar colors (background, statusline) from the local Sway config
• Applied parsed colors to the theme's idle_bg and idle_fg fields
• Added necessary Rust glue code with minimal footprint

Config Usage

To enable this, add to your config.toml:

[sway_integration]
use_sway_bar_colors = true