Translate theme selector

src/locales/en.json

@@ -379,5 +379,19 @@
     "furtherSteps": {
       "string": "Further steps for Linux"
     }
+  },
+  "theme": {
+    "system": {
+      "string": "Use system theme",
+      "context": "Option to choose dark/light mode based on whatever the global system theme is"
+    },
+    "dark": {
+      "string": "Dark",
+      "context": "Dark mode option"
+    },
+    "light": {
+      "string": "Light",
+      "context": "Light mode option"
+    }
   }
 }

src/packager/SelectTheme.svelte

@@ -1,9 +1,10 @@
 <script>
   import {theme} from './stores';
+  import {_} from '../locales';
 </script>
 
 <select bind:value={$theme}>
-  <option value="system">Use system theme</option>
-  <option value="light">Light</option>
-  <option value="dark">Dark</option>
+  <option value="system">{$_('theme.system')}</option>
+  <option value="light">{$_('theme.light')}</option>
+  <option value="dark">{$_('theme.dark')}</option>
 </select>