Adding some missing i18n strings

frontend/src/app/components/hashrate-chart/hashrate-chart.component.ts

@@ -223,7 +223,7 @@ export class HashrateChartComponent implements OnInit {
       legend: (this.widget || data.hashrates.length === 0) ? undefined : {
         data: [
           {
-            name: 'Hashrate',
+            name: $localize`:@@79a9dc5b1caca3cbeb1733a19515edacc5fc7920:Hashrate`,
             inactiveColor: 'rgb(110, 112, 121)',
             textStyle: {
               color: 'white',
@@ -234,9 +234,9 @@ export class HashrateChartComponent implements OnInit {
             },
           },
           {
-            name: 'Difficulty',
+            name: $localize`:@@25148835d92465353fc5fe8897c27d5369978e5a:Difficulty`,
             inactiveColor: 'rgb(110, 112, 121)',
-            textStyle: {
+            textStyle: {  
               color: 'white',
             },
             icon: 'roundRect',
@@ -290,7 +290,7 @@ export class HashrateChartComponent implements OnInit {
       series: data.hashrates.length === 0 ? [] : [
         {
           zlevel: 0,
-          name: 'Hashrate',
+          name: $localize`:@@79a9dc5b1caca3cbeb1733a19515edacc5fc7920:Hashrate`,
           showSymbol: false,
           symbol: 'none',
           data: data.hashrates,
@@ -302,7 +302,7 @@ export class HashrateChartComponent implements OnInit {
         {
           zlevel: 1,
           yAxisIndex: 1,
-          name: 'Difficulty',
+          name: $localize`:@@25148835d92465353fc5fe8897c27d5369978e5a:Difficulty`,
           showSymbol: false,
           symbol: 'none',
           data: data.difficulty,