Add Nette\Http\FileUpload::getImageSize() stub with return type narrowed

PR'd phpstan/phpstan-nette#166 and this can be removed once the PR is merged and deployed.

app/phpstan.neon

@@ -10,6 +10,8 @@ parameters:
 		- phpt
 	level: 9
 	checkMissingOverrideMethodAttribute: true
+	stubFiles:
+		- stubs/Nette/Http/FileUpload.phpstub
 
 includes:
 	- phar://phpstan.phar/conf/bleedingEdge.neon

app/stubs/Nette/Http/FileUpload.phpstub

@@ -0,0 +1,18 @@
+<?php
+// Copied from https://github.com/phpstan/phpstan-nette/pull/166,
+// can be removed once the PR is merged and released.
+
+namespace Nette\Http;
+
+class FileUpload
+{
+
+	/**
+	 * @return array{0:positive-int, 1:positive-int}|null
+	 */
+	public function getImageSize(): ?array
+	{
+		// nothing
+	}
+
+}