docs: add new VueFire logo (#589)

* feat: add new VueFire logo

* fix: fix alt text

* chore: update logo with latest version

Closes #158

Author: sarahdayan

README.md

@@ -1,4 +1,4 @@
-<p align="center"><a href="https://vuefire.vuejs.org" target="_blank" rel="noopener noreferrer"><img width="100" src="https://vuefire.vuejs.org/firebase-logo.svg" alt="Vue logo"></a></p>
+<p align="center"><a href="https://vuefire.vuejs.org" target="_blank" rel="noopener noreferrer"><img width="100" src="https://vuefire.vuejs.org/vuefire-logo.svg" alt="VueFire logo"></a></p>
 
 <h1 align="center">Vuefire & Vuexfire</h1>
 <p align="center">