Improving doc comments syntax highlighting in hovering

After #97 and #525 have been merged we can provider basic syntax highlight when hovering.

Current state

Apparently vscode does not detect ```res example as rescript syntax. In markdown highlighting works.

Proposal

Convert ```res example to rescript. This can be done on the client side `client/src/extension.ts`, but I'm more +1 to do it in analysis bin as it wouldn't affect other clients.

As the return is markdown we could create sections using the word after ```res?

From:

```res example

To:

## Example\n```rescript

Example:

From:

Constructs a RegExp object (Js.Re.t) from a `string`.
Regex literals `%re("/.../")` should generally be preferred, but `fromString`
is useful when you need to dynamically construct a regex using strings,
exactly like when you do so in JavaScript.

```res example
let firstReScriptFileExtension = (filename, content) => {
  let result = Js.Re.fromString(filename ++ "\.(res|resi)")->Js.Re.exec_(content)
  switch result {
  | Some(r) => Js.Nullable.toOption(Js.Re.captures(r)[1])
  | None => None
  }
}

// outputs "res"
firstReScriptFileExtension("School", "School.res School.resi Main.js School.bs.js")
```

To:

Constructs a RegExp object (Js.Re.t) from a `string`.
Regex literals `%re("/.../")` should generally be preferred, but `fromString`
is useful when you need to dynamically construct a regex using strings,
exactly like when you do so in JavaScript.

## Example

```rescript
let firstReScriptFileExtension = (filename, content) => {
  let result = Js.Re.fromString(filename ++ "\.(res|resi)")->Js.Re.exec_(content)
  switch result {
  | Some(r) => Js.Nullable.toOption(Js.Re.captures(r)[1])
  | None => None
  }
}

// outputs "res"
firstReScriptFileExtension("School", "School.res School.resi Main.js School.bs.js")
```

Below an example after convert res to rescript. Note: indentation at the beginning of the line are preserved, we must remove them.

Beginne mit der Untersuchung der Hover-Verarbeitung in client/src/extension.ts und des im Issue vorgeschlagenen analysis bin-Pfads. Verfolge, wie Hover-Markdown zusammengesetzt wird, einschließlich umzäunter Blöcke und Einrückung. Als erledigt gilt, wenn res example-Blöcke als rescript-Syntax mit einem Example-Abschnitt gerendert werden und die Einrückung des erhaltenen Inhalts wie erforderlich entfernt wird.