docs(integ-runner): add missing options (#28969)

### Reason for this change
Include an explanation of the option in the documentation to make it easier for users to understand.

### Description of changes
This PR adds an explanation of missing options in README.

### Description of how you validated changes

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: sakurai-ryo

packages/@aws-cdk/integ-runner/README.md

@@ -97,6 +97,12 @@ If not, changes cannot be compared across systems.
   - `go`:
     - File RegExp: `^integ_.*\.go$`
     - App run command: `go run {filePath}`
+- `--list` (default=`false`)
+  List tests instead of running them.
+- `--inspect-failures` (default=`false`)
+  Keep generated snapshots when differences exist in snapshot comparisons.
+- `--max-workers` (default=`16`)
+  The max number of workerpool workers to use when running integration tests concurrently.
 
 Example: