Move src/docs to src/web/docusaurus

[menghif]

Issue This PR Addresses

Partial work for #2993
Fixes #3326

Type of Change

• Bugfix: Change which fixes an issue
• New Feature: Change which adds functionality
• Documentation Update: Change which improves documentation
• UI: Change which improves UI

Description

This PR moves our docs from src/docs to src/web/docusaurus. I have also updated CI for docusaurus.

Steps to test the PR

Checklist

• Quality: This PR builds and passes our npm test and works locally
• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not (if applicable)
• Documentation: This PR includes updated/added documentation to user exposed functionality or configuration variables are added/changed or an explanation of why it does not(if applicable)

[gitpod-io]