Bugfix/kbd adoc bad input

[cscheid]

Calling the kbd shortcode in asciidoc format with bad inputs would cause a crash. This turns the crash into a shortcode error message.

[cderv]

As I looked into that, as we are producing some RawInline, I would have expected a pandoc.write so that proper escaping for ASCIIDOC is used
We have stringEscape(shortcutText, FORMAT) for that

quarto-cli/src/resources/filters/common/string.lua

Lines 35 to 39 in ebc4b52

	-- escape string by converting using Pandoc
	function stringEscape(str, format)
	local doc = pandoc.Pandoc({pandoc.Para(str)})
	return pandoc.write(doc, format)
	end

[cscheid]

Actually, the previous code was correct, and we can't use pandoc.write. + needs to stay as + according to the docs, and pandoc.write produces {plus}.