Support Hurl unicode literal in multiline string
As written in the Hurl grammar, multiline strings and one line strings should support Hurl unicode literals:
POST https://foo.com
```
Un bon caf\u{e9}!
```
equivalent to:
POST https://foo.com
```
Un bon café!
```
One line strings should be OK also:
POST https://foo.com
`Un bon caf\u{e9}!`
equivalent to
POST https://foo.com
`Un bon café!`
Multiline strings with "Langage hint" also work:
POST https://foo.com
```json
{
"word" :"Un bon ca\u{e9}!"
}
```
While, in the last case, it should be more idiomatic to use a JSON body with JSON unicode literals:
POST https://foo.com
{
"word" :"Un bon ca\u00e9!"
}
Note: we don't support Hurl unicode literals in JSON body as it may add confusion with JSON unicode literals
\u{e9}vs\u00e9
As discussed, escapes won't be interpreted in a multiline string body by default.
Escaping will be triggered explicitly with the escape attribute.
```escape
this is a tab <\t>
```
On the contrary, variables will be evaluated by default.
They will not be evaluated with the novariable attribute.
```novariable
Hello {{name}}!
```
While multiline strings supports escape and novariale attribute now, we're going to deprecate them.