Remove `nextgroup=shComment` from the `shEscape` syntax pattern.
This was causing `#` characters after escape sequences inside
double-quoted strings to be misinterpreted as comments, breaking
highlighting for the rest of the file.
Add a test case for escaped characters followed by # in double quotes.
fixes: #19053closes: #19414
Signed-off-by: Bozhidar Batsov <bozhidar@batsov.dev>
Signed-off-by: Christian Brabandt <cb@256bit.org>