use mime_guess

Signed-off-by: kernelkind <kernelkind@gmail.com>

crates/notedeck/Cargo.toml

@@ -27,6 +27,7 @@ puffin_egui = { workspace = true, optional = true }
 sha2 = { workspace = true }
 bincode = { workspace = true }
 ehttp = {workspace = true }
+mime_guess = { workspace = true }
 
 [dev-dependencies]
 tempfile = { workspace = true }