feat: display warning log message when it can not parse config

[is2ei]

fix #662

Short description of what this resolves:
This PR changes it to display a warning log message when it can not parse config.

Proposed changes:
Display warning log message

[is2ei]

Sorry but I would fix tests.

[codecov]

Codecov Report

Merging #893 (f16d78c) into master (5a17fdd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #893   +/-   ##
=======================================
  Coverage   96.68%   96.68%           
=======================================
  Files           2        2           
  Lines        1627     1627           
  Branches      291      291           
=======================================
  Hits         1573     1573           
  Misses         54       54           

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[is2ei]

Tests are fixed. Could you review it?

[is2ei]

@thedaviddias
Hi, would this change be acceptable? If not, I'll close this PR.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[coliff]

@thedaviddias you approved this so can it be merged ?

[thedaviddias]

@thedaviddias you approved this so can it be merged ?

Yes, it can. @is2ei Can you just fix the conflict?

[is2ei]

@thedaviddias

I fixed the conflict.
The test below fails, but I'm not sure it relates to this change.
https://github.com/htmlhint/HTMLHint/runs/7480344654?check_suite_focus=true