fix: error on isError due to changes of output format of npm view

[sotarok]

Overview

The Following error occurred when the specific condition:

% npx can-npm-publish --verbose
`npm view` command's exit code: 0
`npm view` stdoutJSON 0.0.1
`npm view` stderrJSON null
/can-npm-publish/lib/can-npm-publish.js:111
            return json && "error" in json;
                                   ^

TypeError: Cannot use 'in' operator to search for 'error' in 0.0.1
    at isError (/can-npm-publish/lib/can-npm-publish.js:111:36)
    at is404Error (/can-npm-publish/lib/can-npm-publish.js:114:20)
    at ChildProcess.<anonymous> (/can-npm-publish/lib/can-npm-publish.js:148:17)
    at ChildProcess.emit (node:events:394:28)
    at maybeClose (node:internal/child_process:1064:16)
    at Socket.<anonymous> (node:internal/child_process:450:11)
    at Socket.emit (node:events:394:28)
    at Pipe.<anonymous> (node:net:672:12)

Reproduce and conditions

In npm 7, the output format has been changed from array of single version like [ "0.0.1" ] to a single string like "0.0.1" when the package has only one version.

Conditions:

• The package only one published version
• npm 7

The response format of npm view PACKAGE_NAME --json

% npm view PACKAGE_NAME versions --json
"0.0.1"

In npm 6, the same command shows following output:

% npm view PACKAGE_NAME versions --json
[
  "0.0.1"
]

[azu]

Thanks!

I've released v1.3.6