[WebUI] Reddit video generation

[MatteoFasulo]

Adapt the work of @duozokker into the WebUI ("reddit" page) allowing the user to modify the json file (as for main video.json file)

Expected behavior User should be able to select which video to generate and modify the json file directly from the WebUI

Screenshots WebUI

Additional context (From discussion #26) Additional features (=> @YotomiY) will be a transition with "follow" pop-up animation, reddit (submission) title on screen with post box template containing the submission content

Target branch is reddit