On Windows, the pdf-extension needs improved attribute escapement.

On Windows, the existing shellEscape function in Assembler's runCommand function only wraps argv values in double quotation marks if the value has a space. No consideration is given to shell special characters when spaces are not involved.

When I define an attribute whose value is an HTML entity, the "pdf-extension" passes that attribute unescaped to Asciidoctor PDF on the command line.

For example:

:nl: 


results in Asciidoctor PDF being invoked with:

... -a nl=
 ...

Using Powershell, that sequence causes the Asciidoctor PDF invocation to attempt execution of a program named #10.