[Maintenance] Configure .gitattributes (#421)

| Q               | A
| --------------- | -----
| Branch?         | 1.7
| Bug fix?        | kinda
| New feature?    | no
| Related tickets | related #412

Author: Rafikooo

.gitattributes

@@ -0,0 +1,20 @@
+/.github                        export-ignore
+/etc                            export-ignore
+/spec                           export-ignore
+/tests/Application              export-ignore
+/tests/DataFixtures             export-ignore
+/tests/DependencyInjection      export-ignore
+/tests/Integration              export-ignore
+/tests/Service                  export-ignore
+/tests/Unit                     export-ignore
+.editorconfig                   export-ignore
+.gitattributes                  export-ignore
+.gitignore                      export-ignore
+behat.yml.dist                  export-ignore
+ecs.php                         export-ignore
+node_modules                    export-ignore
+phpspec.yml.dist                export-ignore
+phpstan.neon.dist               export-ignore
+phpunit.xml.dist                export-ignore
+rector.php                      export-ignore
+symfony.lock                    export-ignore

.gitignore

@@ -1,4 +1,5 @@
 /vendor/
+/var/
 /node_modules/
 /composer.lock