feat(exercises): add solution for 17_pointers (#124)

Co-authored-by: shravan || श्रvan <mrshravankumarb@gmail.com>

Author: sidharth-chauhan

internal/exercises/solutions/17_pointers/pointers.go

@@ -0,0 +1,9 @@
+package pointers
+
+func modifyValue(ptr *int) *int {
+	if ptr == nil {
+		return nil
+	}
+	*ptr = 100
+	return ptr
+}

internal/exercises/templates/17_pointers/pointers.go

@@ -1,10 +1,8 @@
 package pointers
 
-// TODO:
-// - Modify the value pointed to by the incoming *int.
-// - Return the same pointer after updating the underlying value.
-// - Avoid allocating any new memory; operate in place.
-
+// TODO: Modify the value pointed to by the incoming *int.
+// Return the same pointer after updating the underlying value.
+// Avoid allocating any new memory; operate in place.
 func modifyValue(ptr *int) *int {
 	// TODO: implement mutation via pointer
 	return ptr