Bump MoonDeck to 1.8.4

[FrogTheFrog]

MoonDeck

• Added a MoonDeck button to demo pages.
• Marked "pass to buddy" resolution change feature as deprecated. Still enabled on linux for now, but disabled on Windows, because Sunshine can now do this on its own (on Windows).
• Updated the lock-file to v9.

Task Checklist

Developer

• I am the original author or an authorized maintainer of this plugin.
• I have abided by the licenses of the libraries I am utilizing, including attaching license notices where appropriate.

Plugin

• I have verified that my plugin works properly on the Stable and Beta update channels of SteamOS.
• I have verified my plugin is unique or provides more/alternative functionality to a plugin already on the store.

Backend

• No: I am using a custom backend other than Python.
• No: I am using a tool or software from a 3rd party FOSS project that does not have it's dependencies statically linked.
• No: I am using a custom binary that has all of it's dependencies statically linked.

Community

• I have tested and left feedback on two other pull requests for new or updating plugins.
• I have commented links to my testing report in this PR.

Testing

• Tested on SteamOS Stable or Beta update channel.