Modernize Polyglott for current macOS and Swift toolchains

[Fredmf]

Motivation

• Bring the project up to date so it builds and runs on modern macOS/Xcode toolchains by replacing deprecated APIs and bumping deployment/Swift versions.
• Replace legacy Swift 1/2-era patterns (e.g. NSTask, @NSApplicationMain, old NSSpeechSynthesizer attribute access) with current Swift APIs for maintainability.
• Fix small runtime/asset issues and refresh tests so the project is easier for the community to build and maintain.

Description

• Rewrote AppDelegate to use @main, Process (instead of NSTask), modern NSStatusBar/status item APIs, updated action signatures, safer optional handling, voice list sorting, and escaped voice-name handling when writing defaults in shell commands (AppDelegate.swift).
• Updated voice scanning to use current NSSpeechSynthesizer.attributes(forVoice:) keys and to build the menu with modern APIs and selectors; added error logging around shell invocation and removed brittle manual menu-item index management (AppDelegate.swift).
• Fixed image asset lookup typo and replaced legacy println with modern print in voiceDoc.swift (changed INUK to IN-UK).
• Modernized unit test file to current XCTest patterns (XCTAssertTrue, measure {}) in polyglottTests/polyglottTests.swift.
• Bumped Xcode project settings in polyglott.xcodeproj/project.pbxproj: updated LastUpgradeCheck, set MACOSX_DEPLOYMENT_TARGET = 12.0, and added SWIFT_VERSION = 5.0 across relevant build configurations.
• Added a short note to readme.md announcing the community refresh for current Macs.

Testing

• plutil -lint polyglott/Info.plist polyglottTests/Info.plist passed with OK for both plists.
• Attempted to run xcodebuild -list -project polyglott.xcodeproj but xcodebuild is not available in this Linux execution environment, so a full macOS build/test run could not be executed here.
• Unit test sources were updated to modern APIs but were not executed in this environment due to the lack of Xcode tooling.

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Codex Task