Invalid path error when --project option is missing

[wespen]

When you try to call CLI without the -p parm like
npx apidoc-openapi --src ./src/api/ --out ./docs/api.json

you get back
The "path" argument must be of type string. Received undefined

The problem is in line 44 with path.resolve
apidoc: path.resolve(cwd, program.project)

Stack:

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined
    at validateString (internal/validators.js:121:11)
    at Object.resolve (path.js:980:7)
    at Object.main (/node_modules/@forfuture/apidoc-openapi/src/index.js:44:18)

Let me know if you would accept the pull request.

[GochoMugo]

It surely is not clear that the parameter is required.

What changes do you suggest?

[wespen]

Handle it as optional and skip path resolving.
apidoc is in if case later in the code.