feat: add Expedia plugin icon

[Patrick-Erichsen]

Description

Adds an icon URL to openclaw.plugin.json so ClawHub/OpenClaw catalog surfaces can render Expedia artwork for this plugin.

The value uses the Expedia logo from Simple Icons as a concrete example:

"icon": "https://cdn.simpleicons.org/expedia"

Any HTTPS image URL can be used for this field; it does not need to come from Simple Icons.

Motivation and Context

Recent OpenClaw manifest updates added icon metadata for bundled plugins so marketplace/catalog cards can show brand artwork when a plugin declares it. This applies the same manifest convention to the Expedia OpenClaw plugin.

How Has This Been Tested?

• Parsed openclaw.plugin.json with Node:

openclaw.plugin.json parses

• Checked the icon URL response:

HTTP/2 200
content-type: image/svg+xml

• Ran git diff --check successfully.

Screenshots (if appropriate):

N/A - manifest metadata only.

Checklist:

• My code follows the code style and contribution guidelines of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.