implement brush cost gauges

they're a little ugly at the moment, and can be a little useless for most simple brushes, but whatever we'll make them better later

static/haku.js

@@ -257,4 +257,24 @@ export class Haku {
 
         return { status: "ok" };
     }
+
+    get astSize() {
+        if (this.#pBrush != 0) {
+            return w.haku_stat_ast_size(this.#pBrush);
+        } else {
+            return 0;
+        }
+    }
+
+    get numRefs() {
+        return w.haku_stat_num_refs(this.#pInstance);
+    }
+
+    get remainingFuel() {
+        return w.haku_stat_remaining_fuel(this.#pInstance);
+    }
+
+    get remainingMemory() {
+        return w.haku_stat_remaining_memory(this.#pInstance);
+    }
 }