Reduce package size (#11)

* Remove unneeded files from the export, reduce overall size

* Added some other items

.gitattributes

@@ -1,2 +1,11 @@
 # Auto detect text files and perform LF normalization
 * text=auto
+/.github export-ignore
+/tests export-ignore
+/.gitattributes export-ignore
+/.gitignore export-ignore
+/phpstan.neon export-ignore
+/phpunit.xml export-ignore
+/rector.php export-ignore
+/.php-cs-fixer.php export-ignore
+/composer.lock export-ignore