Copy to Clipboard > Tex commands doesn't trim newlines

[falsandtru]

Issue Summary

Show Math As > Tex commands > Copy to Clipboard trims \n but Copy to Clipboard > Tex commands doesn't. Both commands should trim \n.

Steps to Reproduce:

      displayMath: [['$$', '$$']],

$$
E = mc^2
$$

1. Right click.
2. Click Copy to Clipboard > Tex commands.
3. The copied text has \n at the first and the last.

Any other information you want to share that is relevant to the issue
being reported. Especially, why do you consider this to be a bug? What
do you expect to happen instead?

Technical details:

• MathJax Version: 3.1.2
• Client OS: Win10
• Browser: Chrome 85.0.4183.121

Supporting information:

• Please supply a link to a (live) minimal example page, when possible.
• If your issue is with the display of the mathematics produced by MathJax, include a screen snapshot that illustrates the problem, when possible.
• Check your browser console window for any error messages, and in crude them here.
• Include the MathJax configuration you are using, and the script tag that loads MathJax itself.

<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/3.1.2/es5/tex-chtml.min.js" integrity="sha512-OEN4O//oR+jeez1OLySjg7HPftdoSaKHiWukJdbFJOfi2b7W0r0ppziSgVRVNaG37qS1f9SmttcutYgoJ6rwNQ==" crossorigin="anonymous"></script>

[dpvc]

Thanks for the suggestion. it makes sense to do the trimming for the clipboard.