Update regex for empty nodes for also excluding img

[HolgerAusB]

Some websites using closing </img> nodes which is not defined in HTML. In most cases, this results in <img src="..."></img> which is currently detected as empty node and therefore removed by graby. So all images from those domains can currently not be fetched by wallabag.

This will fix lot of issues in wallabagger for missing images.

example: https://taz.de/Stadtbilddebatte-wird-praktisch/!6136666/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.71%. Comparing base (f2d2e0b) to head (214852a).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #381      +/-   ##
============================================
- Coverage     95.80%   95.71%   -0.10%     
  Complexity      691      691              
============================================
  Files            17       17              
  Lines          1931     1890      -41     
============================================
- Hits           1850     1809      -41     
  Misses           81       81              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[HolgerAusB]

Sorry @j0k3r just saw, it is a duplicate of #352
Have you thought about that?

I am not a coder, I can RegEx, I can read and edit simple php. I can not write a test for my fix. And I think that also applies to @Strubbl