docs: fix linking to npmjs.com (vuejs#5426) [ci skip]

Rolanddoda · web-flow · commit 75017b22d904 · 2020-04-26T23:52:45.000+08:00
diff --git a/docs/dev-guide/plugin-dev.md b/docs/dev-guide/plugin-dev.md
@@ -861,7 +861,7 @@ The logo should be a square non-transparent image (ideally 84x84).
 
 ## Publish Plugin to npm
 
-To publish your plugin, you need to be registered an [npmjs.com](npmjs.com) and you should have `npm` installed globally. If it's your first npm module, please run
+To publish your plugin, you need to be registered an [npmjs.com](https://www.npmjs.com) and you should have `npm` installed globally. If it's your first npm module, please run
 
 ```bash
 npm login
