Add type checking docs

Author: patriksvensson

docs/language/casting.md renamed to docs/language/type-casting.md

@@ -2,7 +2,9 @@
 sidebar_position: 50
 ---
 
-# Casting
+# Type Casting
+
+## Casting
 
 ```mew
 // This line declares a variable `i` and initializes 
@@ -13,7 +15,5 @@ let i: any = 32;
 
 // This line attempts to cast the value stored in `i` to the 
 // data type `i32` which is a signed 32-bit integer. 
-let j= i as i32;
-```
-
-In summary, casting in this code snippet involves converting a value from the generic `any` type to the specific `i32` type, ensuring that the variable `j` is of the desired data type. This casting operation is possible because the original value in `i` is compatible with the target data type `i32`.
+let j = i as i32;
+```

docs/language/type-checking.md

@@ -0,0 +1,10 @@
+---
+sidebar_position: 55
+---
+
+# Type Checking
+
+```mew
+let i: any = 32;
+let j: i is int;
+```

docs/language/types.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 80
+sidebar_position: 40
 ---
 
 # Types