Allow for using aliases within scetch

[TheBrenny]

[[a= var is aliasVariableName ]]

Aliases would allow us to setup things like [[a= id is object.task.id]] and use the id "variable" throughout the rest of the scetch file.

This would be helpful because then our scetch files become a lot less about scetch and a lot more about the HTML code.

Ideally, this would be scoped to the block (like within an if/each/while block) or file (like components) so we don't accidentally have colliding aliases between files. Perhaps a global alias can be created with [[a= id as aliasVariableName !global ]] or something like that so we can access that variable across the entire scetch.