Docs: Fix broken images and links

docs-src/docs/algo_quantization.md

docs-src/docs/design.md

docs-src/docs/schedule.md

docs-src/docs/tutorial-lang_model.md

docs-src/docs/usage.md

docs/algo_quantization.html

docs/design.html

docs/index.html

docs/schedule.html

docs/search/search_index.json

docs/sitemap.xml

docs/sitemap.xml.gz

docs/tutorial-lang_model.html

docs/usage.html