Template processor hyperlinks

[velPL]

Description

Added setHyperLink() method to Template Processor allowing to insert external hyperlinks.

Fixes #1887 #471

Additional info

• I had to fix code of TOC element class due to phpmd checkup result
• I have no clue what's the cause of code coverage upload error - glad to hear advice on how to fix that on my end

Checklist:

• [x] I have run composer run-script check --timeout=0 and no errors were reported
• [x] The new code is covered by unit tests (check build/coverage for coverage report)
• [x] I have updated the documentation to describe the changes

[PongVL]

Hope this function can be merged to dev branch soon. We need it!

[velPL]

Hello. Are there any chances of feedback/merge ?