Add fee rate display component

frontend/src/app/shared/components/fee-rate/fee-rate.component.html

@@ -0,0 +1,4 @@
+<ng-container *ngIf="rateUnits$ | async as units">
+  <ng-container *ngIf="units !== 'wu'">{{ fee / (weight / 4) | feeRounding:rounding }} <span *ngIf="showUnit" [class]="unitClass">sat/vB</span></ng-container>
+  <ng-container *ngIf="units === 'wu'">{{ fee / weight | feeRounding:rounding }} <span *ngIf="showUnit" [class]="unitClass">sat/WU</span></ng-container>
+</ng-container>

frontend/src/app/shared/components/fee-rate/fee-rate.component.ts

@@ -0,0 +1,26 @@
+import { Component, Input, OnInit } from '@angular/core';
+import { Observable } from 'rxjs';
+import { StateService } from '../../../services/state.service';
+
+@Component({
+  selector: 'app-fee-rate',
+  templateUrl: './fee-rate.component.html',
+  styleUrls: ['./fee-rate.component.scss']
+})
+export class FeeRateComponent implements OnInit {
+  @Input() fee: number;
+  @Input() weight: number = 4;
+  @Input() rounding: string = null;
+  @Input() showUnit: boolean = true;
+  @Input() unitClass: string = 'symbol';
+
+  rateUnits$: Observable<string>;
+
+  constructor(
+    private stateService: StateService,
+  ) { }
+
+  ngOnInit() {
+    this.rateUnits$ = this.stateService.rateUnits$;
+  }
+}