Update markdown_controller.js

[d-buchmann]

Don't handle links as external by default. Instead distiguish internal (relative) and external (absolute) links. That way, if you link to filters in your Part-DB banner, you won't end up with lots of tabs open at the end of the day.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 59.71%. Comparing base (b8d5b83) to head (e5a7ddb). :warning: Report is 228 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #939      +/-   ##
============================================
- Coverage     59.73%   59.71%   -0.02%     
  Complexity     6036     6036              
============================================
  Files           529      529              
  Lines         20588    20588              
============================================
- Hits          12298    12295       -3     
- Misses         8290     8293       +3     

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[jbtronics]

An internal path can be absolute too, but I see no disadvantage in having this change.