Allow types in fenced content of request bodies

[tpluscode]

Problem to solve

To get some syntax support in request bodies I noticed that I can have my IDE (intellij) to recognise known file types as I would in markdown

POST /endpoint
```sparql
Syntax support here \o/
```

Unfortunately, at least in version 1.8.2, the word sparql is included as part of the body

Proposal

Would it be as simple as ignoring trailing characters after the opening triple backtick?

[jcamiel]

Hi @tpluscode we've changed the syntax for the incoming 2.0.0, to support GraphQL body type (see #1000):

POST https://foo.com/graphql
```graphql
query {
  user
}
```

For the moment, I think we make a parsing error if the type is anything apart json, xml, graphql. We may be considering support any string here, or having a broader white list. What do you think @fabricereix?

[fabricereix]

Maybe we should indeed accept any string to be used as doc. If it is really used by Hurl to create a specific body (such as graphql) we could log it in verbose mode.