macros.md: Fix htmlized variant of first source code example

[Flowdalic]

Confusingly, the last part of the first source code example would
appear as

def showExpr(expr: Expr[Boolean])(using Quotes): Expr[String] =
'{ "

     " }

in the htmlized version of the markdown documentation source. Which
reads as follows:

def showExpr(expr: Expr[Boolean])(using Quotes): Expr[String] =
'{ "" } // Better implementation later in this document

This seems to be cause by the usage of angle brackets. Also note that
the code comment does not appear in the htmlized output.

[nicolasstucki]

Suggested change

	'{ [actual implementation later in this document] }
	'{ /* actual implementation later in this document */ }

[Flowdalic]

That will also be eaten by whatever tool transforms the markdown to HTML, just as the other comment (probably all valid Scala comments?). I've no idea why a markdown-to-HTML converter would do that…

[som-snytt]

Handling of angle brackets in code blocks is mangled by scala style at #12734

[Flowdalic]

Probably, it is very common for Markdown code comments to require special handling of angle brackets. But I am talking about code comments, i.e. the \\ comment and /* comment */ which simply disappear in the htmlized output.

[som-snytt]

To confirm, if you remove scala from the triple-backticks, the angle brackets render correctly.

'{ "<some source code>" } // Better implementation later in this document

[som-snytt]

Otherwise it xmlifies as

</span><span id="11" class="">  '{ "
        <some source code>
         " } 
         <span class="hideable">// Better implementation later in this document</span>

        </some></span><pre></pre></code></pre>

Apologies if this was already discussed elsewhere, just mentioning what I noticed this morning.

[nicolasstucki]

The current version makes it readable. We can change it later if we want when the underlying issue is fixed.