docs: update readme

Author: jagnani73

README.md

@@ -47,17 +47,40 @@ This repository contains the logic for decoding a `raw_log_event` of a transacti
         );
         ```
 
-        The method has 3 arguments:
+        The method has 4 arguments:
 
         1. **Event Id**: A case-sensitive string concatenation of the `protocol name` with the `event name` by a `:`.
-        2. **Networks**: An array of all the networks the defined decoding function will run for
+        2. **Networks**: An array of all the networks the defined decoding function will run for.
+        3. **ABI**: The ABI of the contract on which the event exists.
+        4. **Decoding Function**: The actual decoding function, it has 3 arguments passed to it:
+            1. `log_event`: The raw log event that is being decoded.
+            2. `tx`: The transaction object that generated this log.
+            3. `chain_name`: Network to which the log belongs to.
+            4. `covalent_client`: The covalent client created with your covalent API key.
+
+    3.  `fallback`: Creates a fallback function for the specified event name. This function is not linked to any chain or contract. Its declaration is:
+
+        ```ts
+        GoldRushDecoder.fallback(
+            "EventName",
+            ABI as Abi,
+            async (log_event, tx, chain_name, covalent_client): Promise<EventType> => {
+                <!-- decoding logic -->
+            }
+        );
+        ```
+
+        The method has 3 arguments:
+
+        1. **Event Name**: A case-sensitive name of the event to be decoded.
+        2. **ABI**: The ABI of the contract on which the event exists.
         3. **Decoding Function**: The actual decoding function, it has 3 arguments passed to it:
             1. `log_event`: The raw log event that is being decoded.
             2. `tx`: The transaction object that generated this log.
             3. `chain_name`: Network to which the log belongs to.
             4. `covalent_client`: The covalent client created with your covalent API key.
 
-    3.  `decode`: The function that chooses which decoding function needs to be called for which log event. It collects all the decoded events for a transaction and returns them in an array of structured data. It is run when the API server receives a request.
+    4.  `decode`: The function that chooses which decoding function needs to be called for which log event. It collects all the decoded events for a transaction and returns them in an array of structured data. It is run when the API server receives a request.
 
 ### 1. Running the Development Server