* Add a failing test
* Support escaping a mustache with `\`
It is documented in handlebarjs documentation here:
https://handlebarsjs.com/guide/expressions.html#escaping-handlebars-expressions
* Preprocess TextNode to adjust the need of backslashes
Given that template:
```hbs
a non-escaped mustache: \\\{{helper}}
```
Glimmer parser will produce two body nodes:
- a TextNode where `node.chars === "a non-escaped mustache: \\\\"`
- a MustacheStatement for `{{helper}}`
In order to correctly print the input, we need to adjust the TextNode to
`node.chars === "a non-escaped mustache: \\\\\\"`, namely we have to add
a backslash that is removed by Glimmer parser. This is this commit
purpose.
* Add changelog note
Cyrille David
bff049fd96