Add dark mode vim-plug logo and use correct logo version in README (#1267)

README.md

@@ -16,8 +16,15 @@
 </div>
 <br>
 
-<img src="https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.png" height="75" alt="vim-plug">[![build](https://img.shields.io/github/actions/workflow/status/junegunn/vim-plug/test.yml?branch=master)](https://github.com/junegunn/vim-plug/actions/workflows/test.yml?query=branch%3Amaster)
-===
+<h1 title="vim-plug">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="./plug-dark.png">
+    <img src="./plug.png" height="75" alt="vim-plug">
+  </picture>
+  <a href="https://github.com/junegunn/vim-plug/actions/workflows/test.yml?query=branch%3Amaster">
+    <img src="https://img.shields.io/github/actions/workflow/status/junegunn/vim-plug/test.yml?branch=master">
+  </a>
+</h1>
 
 A minimalist Vim plugin manager.