Add type annotation to generated language files map (#29283)

webapp/scripts/gen_lang_imports.mjs

@@ -37,11 +37,16 @@ fs.readdirSync('./channels/src/i18n').forEach(file => {
   }
 });
 
+lines += `
+type TranslationsMap = {
+    [id: string]: string,
+};
+`;
 lines += `\nexport const langIDs = ${JSON.stringify(langIDs)};\n`
 lines += `\nexport const langLabels = ${JSON.stringify(langLabels)};\n`
 
 // To generate the file exports we need to do a bit more work to handle ids with dashes and also output a map of literals rather than strings.
-lines += '\nexport const langFiles = {' + Object.keys(langFiles).reduce((out, id, idx) => {
+lines += '\nexport const langFiles: {[langID: string]: TranslationsMap} = {' + Object.keys(langFiles).reduce((out, id, idx) => {
   if (id.includes('-')) {
     out += `'${id}':${langFiles[id]}`;
   } else {