Add Gorilla Tag VR mod menu plugin source project

[ReedonMenu]

Motivation

• Provide a buildable C# plugin source tree so users can produce a DLL for Gorilla Tag/BepInEx locally.
• Encapsulate VR menu, in-world button interactions, and gameplay toggles (noclip, speed, kick-gun) in a single plugin source.
• Make build instructions explicit so the repo can be used to produce GorillaTagModMenu.dll on a developer machine.

Description

• Add GorillaTagModMenu/Plugin.cs, a full BepInEx plugin implementing a right-hand A-button VR menu, trigger-based in-VR buttons, noclip, speed boost, and kick-gun functionality.
• Add GorillaTagModMenu/GorillaTagModMenu.csproj targeting netstandard2.1 with commented <Reference> placeholders for local Unity/BepInEx/Photon DLLs.
• Update README.md with step-by-step local build instructions and the expected DLL output path (GorillaTagModMenu/bin/Release/netstandard2.1/GorillaTagModMenu.dll).
• Include a lightweight source package (Readonsmenu-source.zip) for easy download from the workspace snapshot.

Testing

• Ran which dotnet to probe the toolchain and found no dotnet installed, so in-container compilation was not possible (expected failure for build step).
• Attempted to fetch the .NET installer with curl https://dot.net/v1/dotnet-install.sh, which returned HTTP 403 and failed to download.
• Executed apt-get update which failed due to repository/proxy HTTP 403 responses, so no runtime installation could proceed.
• Packaged the repository files into a zip using zip to validate file creation and packaging, which succeeded.

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Codex Task