* Add sphinxcontribute-mermaid extension
* Add manual link for mermaid.js
* Load mermaid.js before require.js to avoid errors
* Update documentation guide for the usage of mermaid diagram in our doc
* Resolve error caused by double loaded mermaid.js
* Small fixes
* Small fix based on comments
* Revise toc tree & add draft version for document guide
* Add more contents and revise documentation guide
* Rename new file for documentation guide
* Add some new contents and try to change html tables to plain text tables for generated styles
* Change back to html table with specified css
* Add some new contents and small revision
* Revise contributor index page
* Minor typo fixes for landing page quicklinks
* Revise based on comments
* Add rst card components and small revisions
