Fix docs links (#7005)

* docs: fix broken and redirect links

see #7000

* docs: fix links

see #7000

* docs: merge with master

* docs: fix fnrs and tinyclues logo links

* docs: fix link reference in text

* docs: fix typo

* docs: added back in metaoptimize-qa paragraph

* docs: update language for defunct site

* docs: update stackexchange section

* docs: remove defunct site, move quora to top

* docs: remove defunct link and rearrange links