feat: icon field

[srtaalej]

Summary

Add icon field to display_information in both v1 and v2 manifest schemas to support apps.icon.set functionality (see slackapi/slack-cli#469). The field is an optional string containing a path to the app's icon image file.

Testing

1. Run ./scripts/install_all_and_run_tests.sh — all 6 tests pass
2. Verify the icon field appears in display_information.properties in both schemas/manifest.schema.1.0.0.json and schemas/manifest.schema.2.0.0.json
3. Confirm the field is optional (not added to required array) and accepts any string value

Category

• manifest.schema.json edit
• /schema and/or its core components
• Others

Requirements

• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

[zimeg]

@srtaalej I'm uncertain the display_information field is what the current CLI implementations are expecting:

https://github.com/slackapi/slack-cli/blob/1a7c9495abfaa8ef2c7152ec7a3b06d27a6ff276/internal/shared/types/slack_yaml.go#L24-L28

Would it be possible to share the manifest you used to test this or might I need a particular build otherwise? 🧪 👀