fix: typo in EINVALIDEXECCWD error message (#209)

Author: meesvandongen

lib/definitions/errors.js

@@ -25,7 +25,7 @@ Your configuration for the \`${cmdProp}\` option is \`${stringify(cmd)}\`.`,
 Your configuration for the \`shell\` option is \`${stringify(shell)}\`.`,
   }),
   EINVALIDEXECCWD: ({execCwd}) => ({
-    message: 'Invalid `shell` option.',
+    message: 'Invalid `execCwd` option.',
     details: `The [\`execCwd\` option](${linkify('README.md#options')}) if defined, must be a non empty \`String\`.
 
 Your configuration for the \`execCwd\` option is \`${stringify(execCwd)}\`.`,