feat: custom dom events

[franverona]

#22

• Native CustomEvent dispatching across all lifecycle methods in both implementations
• Full TypeScript types (LoadgoEventMap, augmented HTMLImageElement.addEventListener)
• Interactive demo pages for jQuery and Vanilla JS
• README and CLAUDE.md documentation
• $filter renamed to filter in jQuery _setprogress
• loadgo:options detail is now a shallow copy (prevents internal state mutation)
• setprogress() dispatches loadgo:error on uninitialized elements
• resetprogress() guards against uninitialized elements (prevented spurious loadgo:reset)
• Tests for all new error paths (263 passing)

Events

Event	Fires when	event.detail
loadgo:init	init() completes	—
loadgo:error	invalid usage (non-img element, loop/stop on uninitialized, double loop)	{ message: string }
loadgo:options	options() is called as a setter after init	merged LoadgoOptions object
loadgo:progress	setprogress() is called	{ progress: number }
loadgo:complete	progress reaches 100 outside of a loop	{ progress: 100 }
loadgo:reset	resetprogress() is called	{ progress: 0 }
loadgo:start	loop() starts	—
loadgo:cycle	loop completes one full back-and-forth (bounces back to 0)	—
loadgo:stop	stop() is called	{ progress: 100 }
loadgo:destroy	destroy() completes	—