perf: build theme dictionaries in parallel (#11861)

**Related Issue:** N/A

## Summary

✨🏎️✨

Author: jcfranco

packages/calcite-design-tokens/src/build/format/index-file.ts

@@ -25,8 +25,10 @@ export const formatIndexFile: FormatFn = async (args) => {
   const themes = ["light", "dark"] as const;
   const format = options.fileExtension.replace(".", "") as Stylesheet;
 
-  const darkDictionary = await dark.getPlatformTokens(options.platform, { cache: true });
-  const lightDictionary = await light.getPlatformTokens(options.platform, { cache: true });
+  const [darkDictionary, lightDictionary] = await Promise.all([
+    dark.getPlatformTokens(options.platform, { cache: true }),
+    light.getPlatformTokens(options.platform, { cache: true }),
+  ]);
 
   const commonVarFormat = "css";
   const varLists = {

packages/calcite-design-tokens/src/build/transforms/value/merge-value.ts

@@ -17,8 +17,10 @@ const transformValueMergeValues: ValueTransform["transform"] = async (token, con
   }
 
   if (!dictionaries) {
-    const darkDictionary = await dark.getPlatformTokens(options.platform, { cache: true });
-    const lightDictionary = await light.getPlatformTokens(options.platform, { cache: true });
+    const [darkDictionary, lightDictionary] = await Promise.all([
+      dark.getPlatformTokens(options.platform, { cache: true }),
+      light.getPlatformTokens(options.platform, { cache: true }),
+    ]);
 
     dictionaries = { dark: darkDictionary, light: lightDictionary };
   }