Add phpstan baseline config

phpstan-baseline.neon

@@ -0,0 +1,31 @@
+parameters:
+	ignoreErrors:
+		-
+			message: "#^Parameter \\#1 \\$callback of function array_map expects \\(callable\\(array\\<int, string\\>\\|string\\)\\: mixed\\)\\|null, 'strtolower' given\\.$#"
+			count: 1
+			path: src/Locale.php
+
+		-
+			message: "#^Parameter \\#1 \\$haystack of function strpos expects string, array\\<int, array\\<int, array\\<int, array\\<int, int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|string given\\.$#"
+			count: 1
+			path: src/Locale.php
+
+		-
+			message: "#^Parameter \\#1 \\$haystack of function strpos expects string, array\\<int, array\\<int, array\\<int, int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|string given\\.$#"
+			count: 2
+			path: src/Locale.php
+
+		-
+			message: "#^Parameter \\#1 \\$string of function substr expects string, string\\|null given\\.$#"
+			count: 2
+			path: src/Locale.php
+
+		-
+			message: "#^Parameter \\#1 \\$subject of static method ipl\\\\Stdlib\\\\Str\\:\\:trimSplit\\(\\) expects string\\|null, array\\<int, array\\<int, array\\<int, array\\<int, int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|string given\\.$#"
+			count: 1
+			path: src/Locale.php
+
+		-
+			message: "#^Parameter \\#1 \\$subject of static method ipl\\\\Stdlib\\\\Str\\:\\:trimSplit\\(\\) expects string\\|null, array\\<int, array\\<int, array\\<int, int\\|string\\>\\|int\\|string\\>\\|int\\|string\\>\\|string given\\.$#"
+			count: 2
+			path: src/Locale.php

phpstan.neon

@@ -1,6 +1,13 @@
+includes:
+	- phpstan-baseline.neon
+
 parameters:
     level: max
 
+    checkFunctionNameCase: true
+    checkInternalClassCaseSensitivity: true
+    treatPhpDocTypesAsCertain: false
+
     paths:
         - src