feat: Add custom window size option

[hdkiller]

This change introduces a new feature that allows users to specify a custom window size when the display mode is set to 'Windowed'. This provides more flexibility for users who want to stream in a window that is not a standard resolution.

The following changes were made:

• Added windowWidth and windowHeight properties to the StreamingPreferences class to store the custom window size.
• Updated the settings UI to include input fields for the custom window dimensions. These controls are only visible when the display mode is set to 'Windowed'.
• Modified the getWindowDimensions() method in the Session class to apply the custom window size during the stream connection process.

• Update: I've changed the settings to be more consistent with the existing elements

[andygrundman]

Looks great to me!