Support Template Syntax

[ysugimoto]

This is a little circumstance from my business, the actual VCL is built by some template engine, then falco could only parse and lint for the built VCL. So it's useful when falco could recognize some template syntax and lint them directly.

Now I'm thinking that we can support the following template engines to lint:

• Mustache ( Handlebars )
• Jinja
• Terraform

At least Terraform template should be supported I think.
Is there other template engines you're using for building production VCLs?