minor #164 Require ctype polyfill (BackEndTea)

This PR was merged into the 6.0-dev branch.

Discussion
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Require ctype polyfill

Fixes #163

Commits
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d114d9b Require ctype polyfill

composer.json

@@ -12,7 +12,8 @@
         "php": ">=7.1.3",
         "symfony/console": "^2.8|^3.4|^4.2",
         "symfony/http-client": "^4.3",
-        "symfony/mime": "^4.3"
+        "symfony/mime": "^4.3",
+        "symfony/polyfill-ctype": "^1.11"
     },
     "bin": ["security-checker"],
     "autoload": {