HTML escape included mermaid files to handle embedded tags

[mgranell]

Summary

Fixes an issue where included mermaid files that had embedded tags failed to render, due to the file being included verbatim into the <div> tag, and embedded html within the mermaid file "breaking out" of the div.

e.g. the following mermaid file will fail:

graph TB
  linkStyle default fill:#ffffff

  14["<div style='font-weight: bold'>This will break</div><div style='font-size: 70%; margin-top: 0px'>[Software System]</div><div style='font-size: 80%; margin-top:10px'>Description<br />with HTML</div>"]

What kind of change does this PR introduce?

Bugfix

For any code change,

• [X] Related documentation has been updated if needed
• [ ] Related tests have been updated or tests have been added There are no tests that test in the include functionality

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [X] No

Related issue, if any:

Tested in the following browsers:

• [X] Chrome
• [ ] Firefox
• [ ] Safari
• [X] Edge
• [ ] IE

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[mgranell]

Test failed due to timeout, not related to change

[sy-records]

Hi, @mgranell Can you provide a screenshot of the before and after comparison? I test here there is no difference.