Don't use simpleMDE editor on mobile devices for 1.13

[mrsdizzie]

simpleMDE doesn't work properly on mobile devices -- We've replaced it with the slightly more working easyMDE in 1.14 but since that change can't be backported to 1.13 we will just disable the editor on mobile here.

Quote reply seemed to assume it had been initialized so I just set it back to text area after to avoid breaking/changing that code on a backport.

[silverwind]

1. Put isMobile into a function in utils.js, making it accessible to other files as well.
2. Not sure how much work it would be but instead of reverting to textarea we should ideally never convert it in first place.

[mrsdizzie]

Its converted back to text because the quote reply seems to rely on it being initialized and doesn't work otherwise. since it is just a 'backport'/quick fix I didn't want to mess with that more then needed

This pr is directly to 1.13 since people didn't want to change it for 1.14 -- could make better changes there maybe

[mrsdizzie]

@silverwind made it a function in utils.js

disabled for code-review and code-review replies also. listed as WIP right now because wiki plain text editing in general is currently broken on 1.13 so unclear how/if this PR would address that.

[mrsdizzie]

OK also fixed bug for switching to plaint text mode on wiki that is present for all 1.13 use (desktop and mobile). Was separately fixed in master from this commit:

374ff60#diff-b50d16bb0041e8bc2ab51127d1231e8ac8bf982ed46e7aaa198da454ef124f95L56-L59

[6543]

🚀

[lunny]

This resulted in #14196. Should we revert this PR?

[zeripath]

I'd argue not - we should fix the IsMobile function instead.

export function isMobile() {
  return /Mobi/.test(navigator.userAgent);
}