Add links to language model quantization notebook in README and docs

README.md

docs-src/docs/tutorial-lang_model_quant.md

docs-src/mkdocs.yml

docs/404.html

docs/algo_earlyexit.html

docs/algo_pruning.html

docs/algo_quantization.html

docs/conditional_computation.html

docs/design.html

docs/index.html

docs/install.html

docs/jupyter.html

docs/knowledge_distillation.html

docs/model_zoo.html

docs/pruning.html

docs/quantization.html

docs/regularization.html

docs/schedule.html

docs/search.html

docs/search/search_index.json