I am out after adding a video element in the template level as it is possible to add a button element like the following;
{action:button}
Is there any way of doing it like this;
{media:video}
I am building a custom template, that's why I should statically give such elements in the HTML so that user can see that there is a video element in the content (it is mandatory) and s/he will edit the source of with the desired URL.
Unfortunately video is not a valid tag.
See:: https://dev.weebly.com/create-the-html-layout-templates.html
The only real option would be to use Weebly's built-in Sections feature, which allows the user to add a video as a background (if that was your intention).
The only other options would be to have them hardcode the URL of the video, in your Theme, have them use the Video Element or point them in the direction of the App Center so they can use an app that provides the feature.