Pull in latest mermaid version while allowing custom versions

[deining]

Making asset URL configurable was discussed more than once in the past. There was even PR #1006 that tried to resolve this issue, better never got merged due to CLA issues.
I myself proposed a solution on this issue with #803 a while ago. Yesterday @huima came up with a question about this issue again. This motivated me to author this PR which implements a quite simple solution for the outstanding issue: users now can simply specify the wanted mermaid version inside project's hugo.yaml:

params:
  mermaid:
    version: 9.3.0

Everything else is transparently done behind the scenes. One can even specify latest in order to pull in the latest released version:

params:
  mermaid:
    version: latest

This PR also adds a paragraph to the mermaid section of the user guide, documenting the newly introduced version parameter in the mermaid config section.

This PR also contributes to #1354 (better GDPR support) in the sense that mermaid script is now pulled in at build time and not at runtime any more.

This PR currently addresses mermaid only. Should be fairly easy to extend this PR so that version of other dependencies (KaTeX, ...) can be specified inside hugo.yaml, too.

This issue fixes #1484.

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Preview: https://deploy-preview-1410--docsydocs.netlify.app/docs/adding-content/diagrams-and-formulae/#diagrams-with-mermaid

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• Closes update mermaid to 10.5.0 #1688 by superseding it
• Contributes to Feature Request: Support offline environments (no internet access) #873

[deining]

Mermaid is at version 10.0.1 now, which is ESM only.
This PR needs to be reworked so that mermaid script is imported as module.

[deining]

This PR was reworked, mermaid script is now imported as module. This allows use use mermaid version 10 and above, right now we are at 10.0.2.

[deining]

Rebased PR to HEAD of branch main and bumped mermaid version to latest released version 10.1.0.

[LisaFC]

@chalin is this something we can pull in without disturbing the Great Bootstrap Upgrade?

[chalin]

I've delayed addressing this PR because it feels like a one-off solution to something we might address as a more global solution to:

• Better GDPR support #1354

[deining]

I've delayed addressing this PR because it feels like a one-off solution

Can you be more specific please? What exactly is missing in my PR?

to something we might address as a more global solution to:

* [Better GDPR support #1354](https://github.com/google/docsy/issues/1354)

I had a look at #1354 again and I'm still on the impression that my PR covers all aspects discussed there. If I missed something however, please advise and I will happily extended and improve my PR so that it covers all desired aspects/functionalities.

[dogmatic69]

I've delayed addressing this PR because it feels like a one-off solution to something we might address as a more global solution to:

• Better GDPR support #1354

In the mean time packages are so outdated we cant do something as simple as document a diagram? Can this get merged in the mean time as it does not change things from a GDPR perspective.

[deining]

Resolved the issues raised and updated documentation to latest mermaid version. From my point of view, this ready for merging.

[chalin]

🚀