[Feature] Multiples choices of backgrounds (YouTube Video, Pexel...)

[YotomiY]

Hello, During the last week I have being testing the project and I think is pretty cool. But there is only one thing in my opinion that's missing: the possibility to choose a background. In the Frontend, you can choose between 3 option:

1. Local video
2. YouTube video (asking the link to download)
3. Pexel (already existing Feature)

Additional context I think this can be great because you can choose manually the background video from a YouTube video (I also want to know if the YouTube part could be detailed a little because it is not very clear where the client_secret.json is obtained from.) Thx @YotomiY

[FujiwaraChoki]

If someone makes a PR, I'll gladly merge it!

[kerta1n]

Starting point would be https://github.com/elebumm/RedditVideoMakerBot