Display reactions as emojis

[kevinaboos]

Currently, reactions are represented as regular strings in an italicized font. This is realized by using the emojis crate to convert an emoji to a string representation, e.g., 🫠 is transformed into its plaintext representation: :melting_face:.

However, this issue is currently blocked, because Makepad doesn't yet support rendering emoji, though this is actively in progress. Once Makepad supports emoji, we can easily make this change to remove the "plaintext-ification" of emojis, and instead just have Makepad render the reaction string as normal

Note that we should keep the design of emojis being represented by the String type, since reactions in Matrix can also just be any arbitrary string of text.