Show IndexedDB-related operations on Splash screen

First half of the progress is for storing the response to IndexedDB (if
a response was received) and the second half for reading the values
from database and casting to ThunderstoreMod objects to be stored in
Vuex.

Add a helper for resetting progress of all subitems on the splash
screen.

src/components/mixins/SplashMixin.vue

@@ -32,6 +32,10 @@ export default class SplashMixin extends Vue {
         return this.requests.reduce((x, y) => x.merge(y));
     }
 
+    resetRequestProgresses() {
+        this.requests.forEach((request) => request.setProgress(0));
+    }
+
     // Get the list of game-specific packages to exclude.
     async getExclusions() {
         this.loadingText = 'Connecting to GitHub repository';
@@ -76,7 +80,9 @@ export default class SplashMixin extends Vue {
             this.loadingText = 'You may be offline or Thunderstore is unavailabe. Checking cache.';
         }
 
+        this.getRequestItem('CacheOperations').setProgress(50);
         await this.$store.dispatch('tsMods/updateMods');
+        this.getRequestItem('CacheOperations').setProgress(100);
 
         if (this.$store.state.tsMods.modsLastUpdated === undefined) {
             this.heroTitle = 'Failed to get mods from Thunderstore and cache';

src/pages/Splash.vue

@@ -159,7 +159,8 @@ export default class Splash extends mixins(SplashMixin) {
     requests = [
         new RequestItem('UpdateCheck', 0),
         new RequestItem('ThunderstoreDownload', 0),
-        new RequestItem('ExclusionsList', 0)
+        new RequestItem('ExclusionsList', 0),
+        new RequestItem('CacheOperations', 0)
     ];
 
     // Ensure that r2modman isn't outdated.
@@ -194,9 +195,7 @@ export default class Splash extends mixins(SplashMixin) {
     }
 
     retryConnection() {
-        this.getRequestItem('UpdateCheck').setProgress(0);
-        this.getRequestItem('ExclusionsList').setProgress(0);
-        this.getRequestItem('ThunderstoreDownload').setProgress(0);
+        this.resetRequestProgresses();
         this.isOffline = false;
         this.checkForUpdates();
     }