* add information changes * update typos * add typo changes * update documents * update chronos.md * add updates * fix rst * add speed-up md * fix broken links and typos, add tutorials
* change branch-2.0 to main * change branch-2.0 to main * colab and github
* add new content to ug of chronos * add link revise * fix broken links * add changes according to comments * add updates * fix typos * change typos