Replace SVGs of LaTeX to just LaTeX

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This should supersede #415

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For light mode:

For dark mode:

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The issue is that this doesn't work for the Sphinx doc yet:

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.77%. Comparing base (08cf8ca) to head (9c8facc).

:exclamation: Current head 9c8facc differs from pull request most recent head ddf95fb. Consider uploading reports for the commit ddf95fb to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #503 +/- ## ======================================= Coverage 77.77% 77.77% ======================================= Files 17 17 Lines 4193 4193 ======================================= Hits 3261 3261 Misses 932 932 ```

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[utensil]

Now we have a very interesting problem that Github doesn't accpet ^ in \texttt but mdinclude will display \^{} as is.

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One improvement of using sphinx_mdinclude is the TOC

v.s.