Add support to diagram priority when overriding.

[sidharthv96]

📑 Summary

Adds support for a priority field when registering diagrams.
Diagrams with higher priority can override ones with lower priority, if they have the same ID.

📏 Design Decisions

Describe the way your implementation works or what design decisions you made if applicable.

📋 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

[codecov]

Codecov Report

Merging #5051 (4a62e7f) into sidv/splitELK (0fec0ef) will decrease coverage by 0.08%.
The diff coverage is 23.52%.

Additional details and impacted files

@@                Coverage Diff                @@
##           sidv/splitELK    #5051      +/-   ##
=================================================
- Coverage          44.36%   44.28%   -0.08%     
=================================================
  Files                 25       25              
  Lines               5218     5236      +18     
  Branches              25       25              
=================================================
+ Hits                2315     2319       +4     
- Misses              2902     2916      +14     
  Partials               1        1              

Flag	Coverage Δ
unit	44.28% <23.52%> (-0.08%)	⬇️

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Files	Coverage Δ
packages/mermaid/src/diagram-api/diagramAPI.ts	57.30% <30.00%> (-1.53%)	⬇️
packages/mermaid/src/diagram-api/detectType.ts	59.79% <20.83%> (-6.48%)	⬇️