[Plugin] Explore features in Backstage (#696)

* Explore plugin

* Fixed styles and props

* Real conent

* Add Lighthouse and fix tests

* Add menu item

* Cleanup

* Change wording

* Update package.json

* Remove dead code

* Update yarn.lock

* Revert change to CODEOWNERS

* Reset yarn.lock to master

* Fix comments

.github/CODEOWNERS

@@ -4,4 +4,4 @@
 # The last matching pattern takes precedence.
 # https://help.github.com/articles/about-codeowners/
 
-* @spotify/backstage-core
+*                @spotify/backstage-core