Use xtask for theme generation

crates/xtask/src/main.rs

@@ -0,0 +1,11 @@
+mod cli;
+
+use schemars::schema_for;
+
+use theme::Theme;
+fn main() {
+    let theme = schema_for!(Theme);
+    let output = serde_json::to_string_pretty(&theme).unwrap();
+    std::fs::create_dir("schemas").ok();
+    std::fs::write("schemas/theme.json", output).ok();
+}