Check succeeds if no configuration file is present

[marcindulak]

The example below uses docker https://github.com/UmbrellaDocs/linkspector/pull/23

1. build the image of the latest linkspector from source

   git clone https://github.com/UmbrellaDocs/linkspector
   cd linkspector
   docker build --build-arg LINKSPECTOR_PACKAGE= -t umbrelladocs/linkspector .

2. run linkspector check on an empty directory

   mkdir empty
   echo '[linkspector](https://github.com/UmbrellaDocs/linkspector-missing)' > empty/test.md
   docker run --rm -it -v $PWD/empty:/app --name linkspector umbrelladocs/linkspector bash -c 'linkspector check'

Output

⠋ Configuration file not found. Using default configuration.
ENOENT: no such file or directory, open '.gitignore'
✨ Success: All hyperlinks in the specified files are valid.

A failure would rather be expected

⠋ Configuration file not found. Using default configuration.
🚫 test.md, https://github.com/UmbrellaDocs/linkspector-missing, 404, 1, null
❌ Error: Some links in the specified files are not valid.