Detect Rime Squirrel “English” Mode (ascii_mode)

[siropkin]

From #19 (comment)

Rime Squirrel repo: https://github.com/rime/squirrel

[siropkin]

Summary info about Rime Squirrel:

Rime is a cross-platform input method primarily for Chinese, with an ascii_mode state that temporarily switches to "ASCII" mode for non-Chinese characters. This state is not specifically an "English" mode but is used for typing Latin characters, numbers, and punctuation. The mode frequently toggles for mixed-script input, and Rime does not natively support external communication with other apps to expose this mode.