chore: baseline pre-existing PHPStan errors

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

phpstan-baseline.neon

@@ -29,3 +29,15 @@ parameters:
 			identifier: postInc.type
 			count: 1
 			path: rrdcleaner.php
+
+		-
+			message: '#^Variable \$calculated_index in isset\(\) always exists and is not nullable\.$#'
+			identifier: isset.variable
+			count: 1
+			path: cli/rrdresize.php
+
+		-
+			message: '#^Offset 1 on array\{non\-falsy\-string, string\} in isset\(\) always exists and is not nullable\.$#'
+			identifier: isset.offset
+			count: 1
+			path: lib/functions.php