Add Vue to supported languages in README

Author: JoosepAlviste

README.md

@@ -77,6 +77,7 @@ language tree (see
 - `php`
 - `html`
 - `svelte`
+- `vue`
 
 This means that in any filetype, if the given languages are injected, this 
 plugin should detect them and correctly set the `commentstring`. For example,