fix: build

src/multi-pid.ts

@@ -9,7 +9,7 @@ export class MultiPID {
   public constructor(channels: number, params: PIDParameters) {
     this.channels = channels;
     this.pids = [];
-    for (var i = 0; i < channels; i++) {
+    for (let i = 0; i < channels; i++) {
       this.pids.push(new PID(params));
     }
   }