v0.6.0

• Breaking Remove deprecated NilAnimationObserver.
• Fix release build of zng-wgt-scroll running out of memory. (#203)
• Implement hot reloading UI nodes.
  • Add zng-ext-hot-reload and zng-ext-hot-reload-proc-macros.
  • Add zng::hot_reload.
  • Add feature="hot_reload" in zng and zng-unique-id.
  • Add hot_reload example.
• Implemented VsCode snippets for common Zng macros, see zng.code-snippets.
• Fix view-process cleanup when app-process panics on init.
• Breaking Remove all Static{Id} unique ID static types.
  • Use static_id! to declare static IDs, the new way is compatible with hot reloading.
  • Removed StaticWindowId, StaticMonitorId, StaticPropertyId, StaticAppId, StaticWidgetId, StaticDeviceId, StaticStateId, StaticCommandMetaVarId, StaticSpatialFrameId.
• Implemented equality/hash for zng::task::SignalOnce.
• Breaking Window::on_close now has args type WindowCloseArgs.
  • Add on_pre_window_close and on_window_close.
• Fix headless windows not receiving close events on app exit request.
• Add std::env::consts::OS to crash error.
• Breaking Refactored multiple system config variables to allow app override.
  • VARS.animations_enabled now is read-write. Added VARS.sys_animations_enabled read-only variable that tracks the system config.
  • KEYBOARD.repeat_config now is read-write. Added KEYBOARD.sys_repeat_config.
  • KEYBOARD.caret_animation_config now is read-write. Added KEYBOARD.sys_caret_animation_config.
  • MOUSE.multi_click_config now is read-write. Added MOUSE.sys_multi_click_config.
  • TOUCH.touch_config now is read-write. Added TOUCH.sys_touch_config.