config: move command schema into schema crate

jay-config-schema/src/command.rs

@@ -0,0 +1,15 @@
+use jay_config::status::MessageFormat;
+
+#[derive(Debug, Clone)]
+pub struct Exec {
+    pub prog: String,
+    pub args: Vec<String>,
+    pub envs: Vec<(String, String)>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Status {
+    pub format: MessageFormat,
+    pub exec: Exec,
+    pub separator: Option<String>,
+}