Add TypeChecker and use its methods wherever possible.

config-serializer/TypeChecker.ts

@@ -0,0 +1,13 @@
+class TypeChecker {
+
+    static firstValidScancode = 1;
+    static lastValidScancode = 231;
+
+    static isUInt8Valid(uint8: number): boolean {
+        return 0 <= uint8 && uint8 <= 255;
+    }
+
+    static isScancodeValid(scancode: number): boolean {
+        return TypeChecker.firstValidScancode <= scancode && scancode <= TypeChecker.lastValidScancode;
+    }
+}