Unit Tests :: links_add_target function and trivial changes

[mdbitz]

Hi:

Attached are some Unit Tests of the formatting function links_add_target. Upon implementation of the tests I found 2 trivial changes with fixes in the included diff. Please let me know if correcting these items is desired or if I should update the test cases to sync with current functionality.

• Replacing existing target="" properties add additional space character
• tags without properties (e.g. <a>) don't get appended with target property

Thank you

[mdbitz]

Unit Tests of links_add_target

[mdbitz]

patch of links_add_target and _links_add_target

[wonderboymusic]

In 26328:

Add unit tests for links_add_target(). Alter the patterns in links_add_target() and _links_add_target() slightly based on learnings after running tests.

Props mdbitz.
Fixes #26164.