build(deps-dev): add infection package to testing purposes

Author: ecastro98

.gitignore

@@ -1,3 +1,4 @@
 .idea/
 vendor/
 .php_cs.cache
+.infection.log

composer.json

@@ -23,6 +23,7 @@
         "friendsofphp/php-cs-fixer": "^2.13",
         "guzzlehttp/psr7": "^1.5",
         "http-interop/http-factory-guzzle": "^1.0",
+        "infection/infection": "^0.11.5",
         "php-http/mock-client": "^1.1",
         "phpspec/prophecy": "~1.0",
         "phpstan/phpstan": "^0.10.7",
@@ -43,6 +44,7 @@
         }
     },
     "scripts": {
+        "infection": "infection",
         "lint": "php-cs-fixer fix --verbose --show-progress=estimating",
         "lint:check": [
             "php-cs-fixer fix --dry-run --verbose --show-progress=estimating"