Refactor math formulae support

[tlylt]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• Others, please explain:

Overview of changes:

Related to #1754
With the latest update in markdown-it-texmath, it is now possible to specify a list of delimiters. Hence, this PR aims to refactor the code to take advantage of the new feature.

• Support dollars and brackets out of the box for math formulae display
• Repurpose the previous texWithDollars plugin into mathDelimiters, for additional support of other delimiters (optional and only for people who actually need it)
• Update documentation
• Update functional tests
• One slightly unrelated change to print out the error stack trace when a plugin fails to load properly, for a better debugging experience

Anything you'd like to highlight / discuss:
nil

Testing instructions:
See documentation and functional tests

• https://deploy-preview-1940--markbind-master.netlify.app/userguide/formattingcontents#math-formulae
• https://deploy-preview-1940--markbind-master.netlify.app/userguide/usingplugins#plugin-mathdelimiters

Proposed commit message: (wrap lines at 72 characters)
Refactor math formulae support

The dollars delimiter for math formulae is currently supported via
a plugin because the markdown-it-texmath package does not
allow for more than one delimiter.

With the latest version update, the markdown-it-texmath package
can now support multiple delimiters.

Let's update the code to specify dollars as a supported delimiter
out of the box for math formulae. Let's also repurpose the
texWithDollars plugin to mathDelimiters for any additional
delimiter addition if any user is interested.

Users can now use dollars and brackets (two popular) delimiters
for math formulae without any configurations.

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Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

[ang-zeyu]

Lgtm otherwise 👍, though if possible @jonahtanjz could take a look as well in case I'm missing anything from the first PR.

[jonahtanjz]

Minor documentation nits. Implementation wise looks good 👍

[jonahtanjz]

LGTM 👍