feat: add max_window_width configuration for tiling windows

[Entharia]

Closes #1266

Adds the feature described here

This pull request adds support for a new max_window_width configuration option, allowing users to set a maximum width for tiling windows—particularly useful for ultra-wide monitors. The implementation ensures that when this option is set, windows will not exceed the specified width and will be centered within the available space. The changes span configuration parsing, workspace state management, and the tiling layout algorithm.

Configuration and Documentation:

• Added the max_window_width option to the general section in both README.md and sample-config.yaml, including documentation and usage examples. [1] [2]
• Updated the GeneralConfig struct and its default implementation to include the new max_window_width field. [1] [2]

Workspace and State Management:

• Propagated the max_window_width setting through workspace creation and reload logic, ensuring each workspace receives and stores this configuration. [1] [2] [3] [4] [5] [6]

Tiling Layout Algorithm:

• Enhanced the tiling layout logic to respect the max_window_width constraint: windows are limited in width and centered if the total width of all windows plus gaps is less than the workspace width. This logic is applied only in horizontal tiling mode. [1] [2] [3] [4]