Update FieldControl.md

Author: Kuldeep Saxena

docs/api/FieldControl.md

@@ -93,3 +93,21 @@ For eg.
 parent: AbstractControl;
 ```
 An instance of FormGroup or FormArray class as a parent control.
+
+##
+```ts
+meta: {[key: string]: any};
+```
+You can pass an object of custom variables to customize your component.
+
+For example:
+
+```ts
+<FieldControl
+  meta={{
+    label: "First Name",
+    placeholder: "Enter your first name"
+  }}
+ ...
+/>
+```