Add editor font size settings

[CopeFiend]

Closes #910

Description

Add options for configuring font size in Editor UI.

Progress

• Add font_size option to Settings Window -> General
• Modify Editor font size through font_size option
• Store modified value in settings.ron
• Clamp values within 8.0px - 48.0px
• Handle text widgets with previously hard-coded values (World Viewer, Tilemap Property, etc.)
• Handle layout scaling with large fonts

Review Guidance

• Would like to know whether it would be better to drill settings: &Settings around, or to store it (if so, where?).
• Would like to whether putting everything in Settings::general is a wise decision.

Screenshots/GIFs

WIP

Checklist

• My code follows the project's code style guidelines
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes don't generate new warnings or errors
• No unsafe code introduced (or if introduced, thoroughly justified and documented)