Update README.md

docs: Improve documentation

docs: Add pictures for documenting

feat: Improve options page style

feat: Improve popup style

feat: update icon

feat: add options page to change pomodoro default time

fix: fix show notification bug

feat: add timer to popup & improve pomodoro functionality

feat: add alarms API and background timer

feat: add save in storage feature

feat: add jsconfig to better chrome API suggestion

feat: add manifest and popup page and icon

Initial commit