Implement WorkerPool, use webkitdirectory input

WorkerPool speeds up processing of plugins by using more cores on separate threads. It terminates and recreates a worker after it finishes a task since web assembly seems to slow down a ton when a worker is reused (maybe memory becomes to large / unfragmented, idk).

I switched to the deprecated input tag with webkitdirectory since it is the only way to load a folder under the program files folder. Drag and drop might be another alternative, but I'd rather have a picker.

workers/PluginsLoader.worker.ts

@@ -1,6 +1,8 @@
 import { hash_plugin, parse_plugin } from "skyrim-cell-dump-wasm";
 
-self.addEventListener('message', async (event: MessageEvent<{ skipParsing?: boolean; filename: string; lastModified: number; contents: Uint8Array}>) => {
+self.postMessage("ready");
+
+self.addEventListener('message', async (event: MessageEvent<{ skipParsing?: boolean; filename: string; lastModified: number; contents: Uint8Array }>) => {
   const { skipParsing, filename, lastModified, contents } = event.data;
   let parsed = undefined;
   let parseError = undefined;
@@ -17,7 +19,7 @@ self.addEventListener('message', async (event: MessageEvent<{ skipParsing?: bool
       }
     }
     const hash = hash_plugin(contents).toString(36);
-    self.postMessage({ filename, lastModified, parsed, hash, parseError, enabled: parsed && !parseError });
+    self.postMessage({ filename, lastModified, parsed, hash, parseError, enabled: parsed && !parseError, timeHashEnd: Date.now() });
   } catch (error) {
     console.error(error);
     self.postMessage(error);