Add doc build artifacts to gitignore (NVIDIA#5187)

During docs building some additional rst files are generated:
* docs/operations/* is used for the per-operator doc pages
* individual indes.rst files are built based on index.py files when the
  example referencing is handled.
Add them to the gitignore.

Signed-off-by: Krzysztof Lecki <[email protected]>

Author: klecki

.gitignore

@@ -24,6 +24,20 @@ docs/fn_table
 docs/fn_to_op_table
 docs/op_autodoc
 docs/fn_autodoc
+docs/dali.png
 docs/nvidia.ico
+docs/operations/*
+docs/examples/audio_processing/index.rst
+docs/examples/custom_operations/index.rst
+docs/examples/general/data_loading/index.rst
+docs/examples/general/expressions/index.rst
+docs/examples/general/general_ops_index.rst
+docs/examples/image_processing/index.rst
+docs/examples/index.rst
+docs/examples/operations_index.rst
+docs/examples/other_index.rst
+docs/examples/sequence_processing/index.rst
+docs/examples/use_cases/index.rst
+docs/examples/use_cases/paddle/index.rst
 .DS_Store
 build-docker-*