add declared type usage to readme

README.md

@@ -90,3 +90,30 @@ The value of the above `result` is:
 ```
 
 All options have JSDoc descriptions [in its source](/index.ts#L82).
+
+
+### When working with generic declared types/interfaces
+
+There's currently a limitation with the inferred return type that `ts-deepmerge` offers, where it's
+unable to take the order of the objects/properties into consideration due to the nature of accepting
+an infinite number of objects to merge as args and what TypeScript currently offers to infer the types.
+The primary use case for the inferred return type is for basic object primitives, to offer something
+more useful as the return type, which does work for a lot of cases.
+
+If you're working with generic declared types though, this can cause the inferred return type to not align
+with what you may expect, as it currently detects every possible value and combines them as a union type.
+When working with declared types, and you know what the final type will align to, simply use the `as` keyword
+as shown in the example below:
+```typescript
+interface IObj {
+  a: string;
+  b: string;
+}
+
+const obj1: IObj = { a: "1", b: "2", };
+const obj2: Partial<IObj> = { a: "1" };
+
+const result = merge(obj1, obj2) as IObj;
+```
+
+More context can be found in [this issue](/~https://github.com/voodoocreation/ts-deepmerge/issues/30).