If introduce backtick, please support multiline string with dedent.
Main problem with d-string is it making string prefix and lexer too complex.
So new string quote is very important chance to introduce new multiline string behavior.
body = ```
<body>
<div>hello</div>
</body>
```
- First newline right after
```is dropped. - Minimum common indent is stripped. In this example, last line (closing
```) indicates how many indent is removed.