replaced var with let/const

lib/single-file/single-file-browser.js

@@ -172,13 +172,13 @@ this.SingleFileBrowser = this.SingleFileBrowser || (() => {
 
 	// https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest
 	function hex(buffer) {
-		var hexCodes = [];
-		var view = new DataView(buffer);
-		for (var i = 0; i < view.byteLength; i += 4) {
-			var value = view.getUint32(i);
-			var stringValue = value.toString(16);
-			var padding = "00000000";
-			var paddedValue = (padding + stringValue).slice(-padding.length);
+		const hexCodes = [];
+		const view = new DataView(buffer);
+		for (let i = 0; i < view.byteLength; i += 4) {
+			const value = view.getUint32(i);
+			const stringValue = value.toString(16);
+			const padding = "00000000";
+			const paddedValue = (padding + stringValue).slice(-padding.length);
 			hexCodes.push(paddedValue);
 		}
 		return hexCodes.join("");