[docs] Tauri CLI could warn about missing simulator

[gronke]

% cargo tauri ios dev "iPhone 15"
/opt/homebrew/bin/ios-deploy
    Info package `ios-deploy` present: true
    Info Starting simulator iPhone 15
    Running BeforeDevCommand (`true`)
    Info Using 10.20.42.51 to access the development server.
    Info detected host target triple "aarch64-apple-darwin"
Building app...
Command line invocation:
    /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -scheme app_iOS -workspace /Users/foo/my-tauri-project/src-tauri/gen/apple/app.xcodeproj/project.xcworkspace/ -sdk iphonesimulator -configuration debug -arch arm64-sim -allowProvisioningUpdates build

User defaults from command line:
    IDEPackageSupportUseBuiltinSCM = YES

Build settings from command line:
    ARCHS = arm64-sim
    SDKROOT = iphonesimulator17.4

2024-03-14 14:24:25.811 xcodebuild[56774:1377744] Writing error result bundle to /var/folders/v3/zxhrh6f9715b87_js_vy4lj40000gn/T/ResultBundle_2024-14-03_14-24-0025.xcresult
xcodebuild: error: Found no destinations for the scheme 'app_iOS' and action build.
    Error command ["xcodebuild"] exited with code 70

The issue is quite common and I assume will be encountered often, so that it might be justified to add a check early in the Tauri ios CLI command. Either installing the missing tools or suggesting users steps to resolve the issue. In this case running:

xcodebuild -downloadPlatform iOS

Tested on dev-branch [ea0242d]

[lucasfernog]

we're currently opening Xcode if no simulator is found, but the idea of installing the iOS platform directly is a good one.