Add a task loader to Vimux

[3ximus]

Hi there. I've been looking for this feature but couldn't find a plugin that did this so I thought vimux was the perfect candidate to have this.

The feature is pretty simple. I just load the .vim/tasks.json file and make the commands available to be selected from a vim popup, or a tmux popup with fzf if available, then I just run them on a vimux runner

Another feature is the autodetection of scripts from package.json to be launched. Ideally, me or someone else could implement more in the future.

I've added a few configuration options and some documentation. Let me know if this is something you'd be okay to have on this plugin.

Cheeers !