[data ingestion] update docs (MystenLabs#16595)

update existing docs:
* add more examples
* fix diagrams
* add documentation for a helper function to setup a single pipeline
workflow

---------

Co-authored-by: ronny-mysten <[email protected]>

docs/content/guides/developer/advanced/custom-indexer.mdx

@@ -34,7 +34,7 @@ The most straightforward stream source is to subscribe to a remote store of chec
 
 ```mermaid
 flowchart LR
-  A("fa:fa-cloud Cloud storage (S3, GCP)");
+  A("fa:fa-cloud Cloud storage(S3, GCP)");
   B[("fa:fa-gears
   Indexer
   daemon")];
@@ -64,7 +64,7 @@ checkpoint-executor-config:
 ```mermaid
 flowchart LR
   subgraph Sui
-    A("fa:fa-server Full node binary");
+    A("fa:fa-server Full node");
     A-->B("fa:fa-folder Local directory");
     B-->C[("fa:fa-gears
     Indexer
@@ -85,10 +85,36 @@ flowchart LR
 Specify both a local and remote store as a fallback to ensure constant data flow. The framework always prioritizes locally available checkpoint data over remote data. It's useful when you want to start utilizing your own Full node for data ingestion but need to partially backfill historical data or just have a failover. 
 
 
-## Example
+## Examples
 
-Here's a basic example of a custom data ingestion worker.
+The Sui data ingestion framework provides a helper function to quickly bootstrap an indexer workflow.
+```rust
+struct CustomWorker;
+
+#[async_trait]
+impl Worker for CustomWorker {
+    async fn process_checkpoint(&self, checkpoint: CheckpointData) -> Result<()> {
+        // custom processing logic
+        ...
+        Ok(())
+    }
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let (executor, term_sender) = setup_single_workflow(
+        CustomWorker,
+        "https://checkpoints.mainnet.sui.io".to_string(),
+        0, /* initial checkpoint number */
+        5, /* concurrency */
+    ).await?;
+    executor.await?;
+    Ok(())
+}
+```
+This is suitable for setups with a single ingestion pipeline where progress tracking is managed outside of the framework.
 
+For more complex setups, refer to the following example:
 ```rust
 struct CustomWorker;
 
@@ -130,5 +156,7 @@ The data ingestion executor can run multiple workflows simultaneously. For each
 
 The concurrency parameter specifies how many threads the workflow uses. Having a concurrency value greater than 1 is helpful when tasks are idempotent and can be processed in parallel and out of order. The executor only updates the progress/watermark to a certain checkpoint when all preceding checkpoints are processed.
 
-Find more examples of custom ingestion pipelines in the [Sui repository](https://github.com/MystenLabs/sui/tree/main/crates/sui-data-ingestion/src/workers).
+Find more examples of custom ingestion pipelines in the Sui repository:
+* Sui data ingestion daemon that runs internal [pipelines](https://github.com/MystenLabs/sui/tree/main/crates/sui-data-ingestion/src/).
+* Sui Name Service's custom [indexer](https://github.com/MystenLabs/sui/tree/main/crates/suins-indexer/src).