Update developer guide

docs/DeveloperGuide.md

@@ -115,6 +115,23 @@ Priorities: High (Must have) - `* * *`, Medium (Good to have) - `* *`, Low (Exte
         * `Invalid reservation time: Restaurant operates between 10:00 and 21:00.` (if outside restaurant hours, considering last reservation at 21:00)
     * Use case resumes at step 1.
 
+
+**Use case: UC04 - Delete Reservation**
+
+**MSS**
+
+1. User requests to delete a reservation by providing an index.
+2. ReserveMate deletes the particular reservation.
+
+    Use case ends.
+
+**Extensions**
+* 1a. The index is invalid.
+  * 1a1. ReserveMate prompts the user to enter a valid index.
+
+    Use case resumes at step 1.
+
+
 **Use case: UC05 - View Schedule**
 
 **MSS**
@@ -137,3 +154,16 @@ Priorities: High (Must have) - `* * *`, Medium (Good to have) - `* *`, Low (Exte
   Use case ends.
 
 *{More to be added}*
+
+
+### Non-Functional Requirements
+1) The system should be primarily command-line based.
+2) A user who can type fast should be able to accomplish tasks faster through this system compared to using 
+one which relies on the mouse.
+3) The system can be used by a user who can understand and write english easily with a minimal learning curve.
+4) The system should use Gradle as a build automation tool, and it must run on any OS which has Java 17.
+5) All reservation details will be stored in a file saved locally which should allow read and write access to the
+system.
+6) The maximum number of reservation the system can hold is 100.
+7) All code pushed into the repository must adhere to checkstyle to ensure readability and maintainability.
+8) The system is designed for a single-user.