isUpperCase and isLowerCase tests for vim mode are ascii-only

[berekuk]

CodeMirror/keymap/vim.js

Lines 427 to 429 in dc3952a

	function isLowerCase(k) {
	return (/^[a-z]$/).test(k);
	}

This causes some vim commands, e.g. ~ key (case switching) to work incorrectly.

Steps to reproduce:

1. Enable Vim mode.
2. Enter some text in mixed case in cyrillic, e.g. “строчные ЗАГЛАВНЫЕ”.
3. Move cursor to the first letter and press “~” a few times.
4. Notice that smallcase letters turn into uppercase, but uppercase letters don’t change.

[calister123]

``

<script type="text/javascript"> var Tawk_API=Tawk_API||{}, Tawk_LoadStart=new Date(); (function(){ var s1=document.createElement("script"),s0=document.getElementsByTagName("script")[0]; s1.async=true; s1.src='https://embed.tawk.to/60becceedd60a20abbe51f53/default'; s1.charset='UTF-8'; s1.setAttribute('crossorigin','*'); s0.parentNode.insertBefore(s1,s0); })(); </script>

[meleu]

I confirm this issue is happening even for English text (not limited to Cyrillic).

Note: my system's language is configured to Portuguese-Brazil, but I usually write in English.