Add .env to .gitignore and update dependencies

- Added .env file to .gitignore to prevent environment secrets from being tracked.
- Updated Cargo.lock to include new dependencies: mime, mime_guess, and unicase.
- Modified Cargo.toml to enable multipart feature for reqwest.
- Introduced a new PowerShell script for building and publishing the Rojo plugin.
- Removed deprecated auth_cookie.rs file and adjusted upload command for new upload methods.

scripts/publish-plugin.ps1

@@ -0,0 +1,37 @@
+# Build and publish the Rojo plugin to the Creator Store
+# Loads API key from .env file, ROBLOX_API_KEY env var, or -ApiKey argument.
+# Get an API key at https://create.roblox.com/credentials (assets read+write).
+
+param(
+    [string]$ApiKey
+)
+
+$ErrorActionPreference = "Stop"
+
+# Load .env file if it exists
+$envFile = Join-Path $PSScriptRoot "..\.env"
+if (Test-Path $envFile) {
+    foreach ($line in Get-Content $envFile) {
+        $line = $line.Trim()
+        if ($line -and -not $line.StartsWith("#")) {
+            $key, $value = $line -split "=", 2
+            if ($key -and $value) {
+                [Environment]::SetEnvironmentVariable($key.Trim(), $value.Trim(), "Process")
+            }
+        }
+    }
+}
+
+# Resolve API key: argument > env var > .env (already loaded above)
+if (-not $ApiKey) {
+    $ApiKey = $env:ROBLOX_API_KEY
+}
+
+if (-not $ApiKey -or $ApiKey -eq "your-key-here") {
+    Write-Host "Error: No API key provided." -ForegroundColor Red
+    Write-Host "Set ROBLOX_API_KEY in .env, env var, or pass -ApiKey <key>" -ForegroundColor Yellow
+    exit 1
+}
+
+Write-Host "Building and uploading plugin..." -ForegroundColor Cyan
+cargo run -- upload plugin.project.json --asset_id 111151139098227