Add Profile button config (PBC)

[TOR968]

Profile Button Config

Adds one or more configurable buttons to Steam community profile pages. Each button links to a URL built from the viewed profile's SteamID64 (e.g. a stats site: https://example.com/profile/{steamId64}). Buttons are managed at runtime from the plugin's settings panel — add, edit, reorder, and remove, no rebuild needed.

Repo: https://github.com/TOR968/profile-button-config

Addresses the earlier review (#195)

This is a resubmission of profile-button-config, reworked to follow the review
guidelines that closed #195:

• webkit-only injection. The button is injected solely by the webkit bundle inside the community browser. The previous CDP fallback, injection-mode selector, and status badge were removed.
• No raw Millennium API. Everything is imported from @steambrew/client / @steambrew/webkit; there is no window.MILLENNIUM_API access in the source.
• Native settings UI. The settings panel uses only Steam native components (Dropdown, TextField, ToggleField, DialogButton, …). The one custom-styled element is the button preview.

Example Setup

example-compressed.mp4

Task Checklist

Developer

• I am the original author or an authorized maintainer of this plugin.
• I have complied with all license requirements for the libraries used, including providing appropriate notices where necessary.
• My plugin is fully open source and does not depend on any external paid services, except for widely trusted and well-known platforms. Additionally, neither I nor anyone associated with me profits from any such services.

Plugin Functionality

• I have tested the plugin on both the Stable and Beta Steam update channels.
• My plugin is unique, or provides additional or alternative functionality to plugins already on the store.

Backend Configuration

• Yes: I use a standard Millennium lua backend in my plugin.
• No: I use custom binaries that or rely on other FOSS projects that aren't written directly using Millennium's lua backend.

Community Contribution

• I have tested and left feedback on two other plugin pull requests.
• I have added links to those feedback comments in this PR.

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Testing Instructions

• Verified by a third party on Steam Client Stable.
• Verified by a third party on Steam Client Beta.