poster alternate text

[Shaxadhere]

I recently used this package in one of my react project and It's really helpful, one thing that kept bothering me was it would show "Tuby Poster" when poster image is not loaded and I decided to add it in your package, I've added a way to add poster alt text from props, this way I can just add video's title in alternate text. I've made small changes, please approve and merge them when you get time.

[Shaxadhere]

@huynhdev24 Can you also merge this PR.

[huynhdev24]

@huynhdev24 Can you also merge this PR.

No

[Shaxadhere]

why