Supplying --no-target results in error

[jasonvasquez]

When using a command such as the following, an error is generated: ebnf2railroad --write-style --no-target my-grammar.ebnf

TypeError: targetFilename?.endsWith is not a function
    at Object.run (/src/myproject/node_modules/ebnf2railroad/src/cli.js:118:38)
targetFilename?.endsWith is not a function

use --help for usage information

(line number may be off by a few there, as I've inserted some local debugging info)

I believe I see the issue, I'll open a PR momentarily.