Allow actions to be deserialized from JSON

Introduce separate macro for implementing 'internal' actions which
are not intended to be loaded from keymaps.

crates/search/Cargo.toml

@@ -20,6 +20,7 @@ workspace = { path = "../workspace" }
 anyhow = "1.0"
 log = "0.4"
 postage = { version = "0.4.1", features = ["futures-traits"] }
+serde = { version = "1", features = ["derive"] }
 
 [dev-dependencies]
 editor = { path = "../editor", features = ["test-support"] }