DOCS: Add blog post - Official Mermaid Chart for Confluence app

[huynhicode]

📑 Summary

This PR adds the lastest Mermaid Chart blog post:

How to Use the official Mermaid Chart for Confluence App

Resolves # n/a

📏 Design Decisions

Design decisions made by the Mermaid Chart team.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.30%. Comparing base (e3c6281) to head (20b0318).
Report is 15 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #5536       +/-   ##
===========================================
+ Coverage    5.73%   77.30%   +71.56%     
===========================================
  Files         278      175      -103     
  Lines       41991    14535    -27456     
  Branches      490      869      +379     
===========================================
+ Hits         2409    11236     +8827     
+ Misses      39582     3091    -36491     
- Partials        0      208      +208     

Flag	Coverage Δ
e2e	82.40% <100.00%> (?)
unit	43.37% <ø> (+37.63%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
packages/mermaid/src/diagrams/block/blockDB.ts	76.47% <100.00%> (+76.47%)	⬆️

... and 275 files with indirect coverage changes