Map IME composition input to Latin characters in non-insert mode.

Is your feature request related to a problem? Please describe.
CJK languages have a character count that far exceeds the number of keys on a keyboard, requiring multiple keystrokes to compose a single character. This makes it impossible to use a simple langmap to control Vim's operations. Traditionally, the autoSwitchInputMethod approach is used to automatically switch input methods, but this method has some drawbacks:

• Unable to maintain consistent input method after switching between insert/normal mode
• Requires additional dependencies (im-select)
• Needs system permissions
• Perceptible delay when switching from insert mode to normal mode (based on my own experience)

Describe the solution you'd like
Map the input of IME composition to the corresponding Latin execution of vim operations.

Additional context
I will provide a PR to implement this feature.

The issue names no files, tests, or entry points. Start by locating the existing input and keybinding handling for non-insert mode, then define how IME composition maps to Latin Vim operations and verify that the behavior avoids the listed input-method switching drawbacks.