Allow liquid variables to be looked in symbol search

[davidwarrington]

I hope I'm using the right terminology with this title.

Basically with the default keybinds, doing cmd + shift + p, then beginning the search with @ allows you to go straight to variables in JS files. Currently in Liquid files we can also use this to find HTML elements, but it would also be nice to search assign tags too. Not entirely necessary as its easy enough to search assign my_variable, but just thought it'd be a neat addition

[panoply]

Agreed. I'll make action on this.