chore: set license to MIT as specified in README and LICENSE file

Include multiple versions of orchestra/testbench to really include support for laravel >= 7

Remove composer.lock as recommended for library projects

Author: Xint0-elab

composer.json

@@ -1,7 +1,7 @@
 {
     "name": "vitorccs/laravel-csv",
     "description": "PHP Laravel package to create CSV files in a memory-optimized way",
-    "license": "GPL-3.0",
+    "license": "MIT",
     "keywords": [
         "laravel",
         "php",
@@ -21,7 +21,7 @@
         "phpunit/phpunit": "^9.5",
         "ext-sqlite3": "*",
         "laravel/legacy-factories": "1.x-dev",
-        "orchestra/testbench": "^6.0"
+        "orchestra/testbench": "^5.0 || ^6.0 || ^7.0 || ^8.0"
     },
     "autoload": {
         "psr-4": {