Update ToUnicode and ToUnicodeEx documentation with new details

[hihayak]

This pull request updates the documentation for the ToUnicode and ToUnicodeEx Windows API functions to clarify the behavior of the wFlags parameter, specifically regarding bit 2 on Windows 10 version 1607 and later. It also documents a known issue affecting Alt+Numeric keypad input when bit 2 is set.

Behavior clarification and known issue documentation:

• Updated the descriptions in both nf-winuser-tounicode.md and nf-winuser-tounicodeex.md to clarify that, on Windows 10 version 1607 and later, setting bit 2 of the wFlags parameter is intended to prevent the function from changing keyboard state. However, a known issue exists where this does not apply to Alt+Numeric keypad input. [1] [2]
• Added an [!IMPORTANT] note in both documentation files explaining that setting bit 2 does not prevent changes to keyboard state for Alt+Numeric keypad input, and that this can affect other calls to the function within the same session or from another thread. [1] [2]

[prmerger-automator]

hihayak : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. Jim Walker (@jwmsft)

[prmerger-automator]

hihayak : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. Jim Walker (@jwmsft)