feature #324 Add polyfill-php81 (nicolas-grekas)

This PR was merged into the 1.21-dev branch.

Discussion
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Add polyfill-php81

https://wiki.php.net/rfc/is_list

Commits
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36fc368 Add polyfill-php81

Author: nicolas-grekas

composer.json

@@ -29,7 +29,7 @@
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {
-            "dev-main": "1.21-dev"
+            "dev-main": "1.22-dev"
         },
         "thanks": {
             "name": "symfony/polyfill",