`{{port}}` variable breaks Treesitter parser

[gorillamoe]

Given this file the parser errors on the {{port}} variable.

@port=3000

POST https://localhost:{{port}}/
accept: application/json
custom-header-date: {{$date}}

Age=24&\
City="Cologne Porz"

[gorillamoe]

This is superseeded by #18. This will fix the current propblems with the variable substitution.