Minecraft wiki entry for Development_versions, associated text: Chat component style now supports font property, which is a resource location for the font in the resource pack. No entry is equivalent to minecraft:default.
Full range of Unicode characters is supported, making it possible to type emojis and other Unicode characters outside of the Basic Multilingual Plane.
However, custom resource packs must be used to display correct characters instead of tofu, due to the lack of these characters in the default font.
Force Unicode option now switches between normal and alternative font (called uniform.json) - no reload needed.