key in version 2 is raw value instead of base64 (which reduces its complexity), made PasteDecryptor support both versions of the format, refactoring method names, replacing var by let / const, reducing zlib compression level from 9 to 7 to half the time spent on compression

js/zlib-1.2.11.js

@@ -5,7 +5,7 @@ let ret;
 async function initialize() {
   if (ret) return ret;
 
-  const COMPRESSION_LEVEL = 9;
+  const COMPRESSION_LEVEL = 7;
   const NO_ZLIB_HEADER = -1;
   const CHUNK_SIZE = 32 * 1024;
   const map = {};