feat(er): allow multi-line relationship labels

[NicolasNewman]

📑 Summary

Allow line breaks to be added to entity relationship labels (using the token <br />)

📏 Design Decisions

• If the token indicating a line break is present, add tspans into the text element per each line of text

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
  (I'll add one if/once this feature gets approval)
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.

Project coverage is 5.20%. Comparing base (5ba5e30) to head (dbd4658).
Report is 16 commits behind head on develop.

Files	Patch %	Lines
packages/mermaid/src/diagrams/er/erRenderer.js	0.00%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #5711      +/-   ##
==========================================
- Coverage     5.21%   5.20%   -0.01%     
==========================================
  Files          322     322              
  Lines        46083   46108      +25     
  Branches       561     561              
==========================================
  Hits          2402    2402              
- Misses       43681   43706      +25     

Flag	Coverage Δ
unit	5.20% <0.00%> (-0.01%)	⬇️

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

Files	Coverage Δ
packages/mermaid/src/diagrams/er/erRenderer.js	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Changes approved	1 added	Aug 25, 2024, 6:04 PM

[changeset-bot]

🦋 Changeset detected

Latest commit: dbd4658

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
mermaid	Minor

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[sidharthv96]

@NicolasNewman code LGTM. Can you please add a visual test?

You can use the same code in demo, having both <br/> and <br /> would be good.