add credits and author (#208)

Author: mightyguava

README.md

@@ -69,3 +69,7 @@ Vim.unmap("jj", "insert");
     // make changes and return new cursor position
   });
 ```
+
+## Credits
+
+This plugin was originally authored by [@mightyguava](https://github.com/mightyguava) (Yunchi Luo) as part of [CodeMirror](https://github.com/codemirror/dev), before being extracted and maintained here.

package.json

@@ -2,6 +2,10 @@
   "name": "@replit/codemirror-vim",
   "version": "6.2.1",
   "description": "Vim keybindings for CodeMirror 6",
+  "author": {
+    "name": "Yunchi Luo",
+    "email": "mightyguava@gmail.com"
+  },
   "scripts": {
     "dev": "vite ./dev",
     "test": "cm-runtests",