Declare our minimum PHP version

So that composer will not update our dependencies to something that
would not work with PHP 8.0. And so that PHPStan analyzes assuming we
are running 8.0

Author: PowerKiKi

composer.json

@@ -12,6 +12,9 @@
         "spreadsheet"
     ],
     "config": {
+        "platform": {
+            "php" : "8.0.99"
+        },
         "sort-packages": true,
         "allow-plugins": {
             "dealerdirect/phpcodesniffer-composer-installer": true

phpstan-baseline.neon

@@ -39,3 +39,8 @@ parameters:
 			message: "#^Offset 3 does not exist on array\\{int, int, int, int\\}\\|array\\{int, int\\}\\.$#"
 			count: 1
 			path: src/PhpSpreadsheet/Worksheet/Validations.php
+
+		-
+			message: "#^Parameter \\#2 \\$value of function ini_set expects string, int given\\.$#"
+			count: 1
+			path: tests/bootstrap.php