Update GitHub links to PL repo (#13849)

* update lightning links in docs

* update links in chlog

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Apply suggestions from code review

Co-authored-by: Rohit Gupta <rohitgr1998@gmail.com>

* Update src/pytorch_lightning/README.md

Co-authored-by: Rohit Gupta <rohitgr1998@gmail.com>

* Update src/pytorch_lightning/README.md

Co-authored-by: Rohit Gupta <rohitgr1998@gmail.com>

* update

* painful

* badges

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update badges

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Rohit Gupta <rohitgr1998@gmail.com>
Co-authored-by: Jirka <jirka.borovec@seznam.cz>
Co-authored-by: Akihiro Nitta <nitta@akihironitta.com>