[4.1] add rel=\"noopener noreferrer\" for target=\"blank\" links

[tecpromotion]

Summary of Changes

during the translation i stumbled across some links with target=_blank without rel="noopener noreferrer".
A global search found only 9 more occurrences.

Testing Instructions

check if the links still work

Actual result BEFORE applying this Pull Request

e.g.
PLG_SYSTEM_JOOA11Y_HEADING_FIRST="The first heading on a page should usually be a Heading 1 or Heading 2. Heading 1 should be the start of the main content section, and is the main heading that describes the overall purpose of the page. Learn more about <a href=\"https://www.w3.org/WAI/tutorials/page-structure/headings/\" target=\"_blank\">Heading Structure.</a>"

Expected result AFTER applying this Pull Request

e.g.
PLG_SYSTEM_JOOA11Y_HEADING_FIRST="The first heading on a page should usually be a Heading 1 or Heading 2. Heading 1 should be the start of the main content section, and is the main heading that describes the overall purpose of the page. Learn more about <a href=\"https://www.w3.org/WAI/tutorials/page-structure/headings/\" target=\"_blank\" rel=\"noopener noreferrer\">Heading Structure.</a>"

Documentation Changes Required

.

[Quy]

I have tested this item ✅ successfully on 2c407d7

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[khu5h1]

I have tested this item ✅ successfully on 2c407d7

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/37014.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/37014.}

[bembelimen]

Thx