UI/UX - New component for difficult adjustment. (#602)

* Add next difficulty blocks.
Add next difficulty target date.
Add next difficulty total progress.
Add ajustment difficulty avg min per block.

* Fix typo.

* Trigger difficulty calculation every 5 seconds.

* Add rxjs timer to difficultyEpoch.

* Fix pipe.

* Fix small bar position.

* Change i18n strings.

* Fix typo.

* Add time-until component.

* Speed up difficultyEpoch timer to 1000 ms.

* Fix values to 2 decimal places.

* Add title to fee and difficulty adjustment cards.

* Add title outside the card.

* Fix title to center position.

* Add other titles.

* Add new transalations strings.
Refactor time span component.

* Fix difficulty adjustment i18n string.
Fix duplicated i18n strings.

frontend/src/app/components/footer/footer.component.html

@@ -19,8 +19,8 @@
       <div class="col">
         <span class="mempoolSize"><ng-container i18n="dashboard.mempool-size|Mempool size">Mempool size</ng-container>:</span>
         <div class="sub-text" *ngIf="(mempoolBlocksData$ | async) as mempoolBlocksData"><span [innerHtml]="mempoolBlocksData.size | bytes"></span> (<ng-container *ngTemplateOutlet="mempoolBlocksData.blocks === 1 ? blocksSingular : blocksPlural; context: {$implicit: mempoolBlocksData.blocks }"></ng-container>)</div>
-          <ng-template #blocksSingular let-i i18n="shared.block">{{ i }} block</ng-template>
-          <ng-template #blocksPlural let-i i18n="shared.blocks">{{ i }} blocks</ng-template>
+        <ng-template #blocksPlural let-i i18n="shared.blocks">{{ i }} <span class="shared-block">blocks</span></ng-template>
+        <ng-template #blocksSingular let-i i18n="shared.block">{{ i }} <span class="shared-block">block</span></ng-template>
       </div>
     </div>
   </div>