Rename package to mattitja/laravel-plausible-proxy

- Rename Composer package to mattitja/laravel-plausible-proxy and
  namespace to Mattitja\LaravelPlausibleProxy
- Point homepage and links to git.mattitja.se
- Forward only User-Agent and visitor IP (X-Forwarded-For) to Plausible
  instead of all request headers
- Forward all event fields and return Plausible's upstream response
- Accept props as array or JSON string
- Drop Laravel 10, upgrade Larastan to 3 and PHPStan plugins to 2
- Remove broken facade alias and dead autoload paths
- Clean up README, issue template and remove invalid FUNDING.yml

phpunit.xml.dist

@@ -16,7 +16,7 @@
     backupStaticProperties="false"
 >
     <testsuites>
-        <testsuite name="MattitjaAB Test Suite">
+        <testsuite name="Mattitja Test Suite">
             <directory>tests</directory>
         </testsuite>
     </testsuites>