env.PWD context variable should resolve to run.command.dir

When using the ${{env.PWD}} context variable expression in a command or environment variable, the expectation is that this expression should evaluate to the resolved run.command.dir path (which defaults to the worktree directory if not specified). Currently, it resolves to the directory in which Antora was launched. That directory is already available through the context variable expression ${{playbook.env.PWD}}.

Another way to think of it is that ${{env.PWD}} should resolve to the same value as $PWD when the command is configured to run in a shell.

Of course, on Windows, PWD is not a default environment variable. So this might be *nix specific. Or perhaps Collector could set the PWD environment variable if not already set.