https links to avoid mixed-content MathJax error

[cben]

https://isnowfy.github.io/simple/editor.html currently doesn't render math because MathJax script is considered mixed-content and doesn't load.
google.com link doesn't matter, changed just to advertise TLS and privacy :-)

[cben]

note this PR is to gh-pages branch, now I see you also have edit src/editor.html on master branch...

[cben]

hmm, blog templates also use http: MathJax URLs. E.g. https://isnowfy.github.io/hello.html gives mixed-content errors.
You're also using cdn.mathjax.org URLs which no longer work.
Closing, will reopen with a more organized fix.

[cben]

Sorry, too busy, not getting to it on my own...
However ping me if you want to fix this (and #26), I'll be happy to make a PR if I know you'll review it.