Adding a global websocket loader observable.

fixes #95

frontend/src/app/components/blockchain/blockchain.component.ts

@@ -1,21 +1,28 @@
-import { Component, OnInit } from '@angular/core';
+import { Component, OnInit, OnDestroy } from '@angular/core';
 import { StateService } from 'src/app/services/state.service';
+import { Subscription } from 'rxjs';
 
 @Component({
   selector: 'app-blockchain',
   templateUrl: './blockchain.component.html',
   styleUrls: ['./blockchain.component.scss']
 })
-export class BlockchainComponent implements OnInit {
+export class BlockchainComponent implements OnInit, OnDestroy {
   txTrackingLoading = false;
   txShowTxNotFound = false;
   isLoading = true;
+  subscription: Subscription;
 
   constructor(
     private stateService: StateService,
   ) {}
 
   ngOnInit() {
-    this.stateService.blocks$.subscribe(() => this.isLoading = false);
+    this.subscription = this.stateService.isLoadingWebSocket$
+      .subscribe((isLoading) => this.isLoading = isLoading);
+  }
+
+  ngOnDestroy() {
+    this.subscription.unsubscribe();
   }
 }