Simplify sanitation

It seems to suffice to use `str downcase` followed by `str kebab-case`
to arrive at the same behavior as the markdown anchor generation.

Using `str downcase` before ensures that CamelCase doesn't get converted
erroneously.

Author: sholderbach

make_release/release-note/notes.nu

@@ -83,13 +83,7 @@ export def write-toc [file: path] {
             let link = (
                 $text
                 | str downcase
-                | str replace -a '`' ''
-                | str replace -a '+' ''
-                | str replace -a '.' ''
-                | str replace -a '?' ''
-                | str replace -a ' ' '-'
-                | str replace -a '_' '-'
-                | str replace -a -r '--+' '-'
+                | str kebab-case
             )
 
             $"($indent)[_($text)_]\(#($link)-toc\)"