expose maxUploadSize and premiumUploadSize via /api/config

lib/load-config.js

@@ -36,5 +36,11 @@ if (!isPositiveNumber(config.defaultStorageLimit)) {
     config.defaultStorageLimit = 50 * 1024 * 1024;
 }
 
+// premiumUploadSize is worthless if it isn't a valid positive number
+// or if it's less than the default upload size
+if (!isPositiveNumber(config.premiumUploadSize) || config.premiumUploadSize < config.defaultStorageLimit) {
+    delete config.premiumUploadSize;
+}
+
 module.exports = config;