Add system design resource from interviewing.io

Update behavioral.md

Update behavioral.md

Update behavioral.md

feat: add coding interviews reads resource

chore: add README.md with brief intro

feat: add behavioral interview page content

fix: all relative links in pages

fix: tip about questions to do in home page

feat: add troubleshooting page content

fix: intro in welcome page

feat: add more resources about system design

feat: add live coding page content

feat: add system design page content

feat: add phase three to home page