Enable custom ICU loading + correct EFIGS keys. (#47419)

Author: ilonatommy

src/Components/Web.JS/src/Platform/BootConfig.ts

@@ -83,5 +83,6 @@ export type ExtendedResourceList = {
 export enum ICUDataMode {
   Sharded,
   All,
-  Invariant
+  Invariant,
+  Custom
 }

src/Components/Web.JS/src/Platform/Mono/MonoPlatform.ts

@@ -493,29 +493,43 @@ function attachInteropInvoker(): void {
 }
 
 function getICUResourceName(bootConfig: BootJsonData, culture: string | undefined): string {
+  if (bootConfig.icuDataMode === ICUDataMode.Custom) {
+    const icuFiles = Object
+      .keys(bootConfig.resources.runtime)
+      .filter(n => n.startsWith('icudt') && n.endsWith('.dat'));
+    if (icuFiles.length === 1) {
+      const customIcuFile = icuFiles[0];
+      return customIcuFile;
+    }
+  }
+
   const combinedICUResourceName = 'icudt.dat';
   if (!culture || bootConfig.icuDataMode === ICUDataMode.All) {
     return combinedICUResourceName;
   }
 
   const prefix = culture.split('-')[0];
-  if ([
-    'en',
-    'fr',
-    'it',
-    'de',
-    'es',
-  ].includes(prefix)) {
+  if (prefix === 'en' ||
+    [
+      'fr',
+      'fr-FR',
+      'it',
+      'it-IT',
+      'de',
+      'de-DE',
+      'es',
+      'es-ES',
+    ].includes(culture)) {
     return 'icudt_EFIGS.dat';
-  } else if ([
+  }
+  if ([
     'zh',
     'ko',
     'ja',
   ].includes(prefix)) {
     return 'icudt_CJK.dat';
-  } else {
-    return 'icudt_no_CJK.dat';
   }
+  return 'icudt_no_CJK.dat';
 }
 
 function changeExtension(filename: string, newExtensionWithLeadingDot: string) {