CI: Force docs warnings to be raised as errors (+ fix all) (#1191)

* add argument to force warn

* fix automodule error

* fix permalink error

* fix indentation warning

* fix warning

* fix import warnings

* fix duplicate label warning

* fix bullet point indentation warning

* fix duplicate label warning

* fix "import not top level" warning

* line too long

* fix indentation

* fix bullet points indentation warning

* fix hooks warnings

* fix reference problem with excluded test_tube

* fix indentation in print

* change imports for trains logger

* remove pandas type annotation

* Update pytorch_lightning/core/lightning.py

* include bullet points inside note

* remove old quick start guide (unused)

* fix unused warning

* fix formatting

* fix duplicate label issue

* fix duplicate label warning (replaced by class ref)

* fix tick

* fix indentation warnings

* docstring ticks

* remove obsolete docstring typing

* Revert "remove old quick start guide (unused)"

This reverts commit d51bb40695442c8fa11bc9df74f6db56264f7509.

* added old quick start guide to navigation

* remove unused  tutorials file

* ignore some modules that got deprecated and are not used anymore

* fix duplicate label warning

* move examples doc and exclude pl_examples from autodoc

* fix formatting for configure_optimizer

* fix no blank line warnings

* fix "see also" labels and add paramref extension

* fix more reference problems

* fix multi-gpu reference

* fix weird warning

* fix indentation and unrecognized characters in code block

* fix warning "... not included in toctree"

* fix PIL import error

* fix duplicate target "here" warning

* fix broken link

* revert accidentally moved pl_examples

* changelog

* stdout

* note some things to know

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>
Co-authored-by: J. Borovec <jirka.borovec@seznam.cz>
Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

docs/source/multi_gpu.rst

@@ -1,5 +1,7 @@
+.. _multi-gpu-training:
+
 Multi-GPU training
-===================
+==================
 Lightning supports multiple ways of doing distributed training.
 
 Preparing your code
@@ -235,7 +237,7 @@ Validation and test step also have the same option when using dp
             ...
 
 Implement Your Own Distributed (DDP) training
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 If you need your own way to init PyTorch DDP you can override :meth:`pytorch_lightning.core.LightningModule.`.
 
 If you also need to use your own DDP implementation, override:  :meth:`pytorch_lightning.core.LightningModule.configure_ddp`.