feat: Display a caps lock indicator on password input

[obany]

Description of change

Displays a caps lock indicator on password input to stop people incorrectly typing passwords in the wrong case.

Links to any relevant issues

Fixes #996 #1021

Type of change

• Enhancement (a non-breaking change which adds functionality)

How the change has been tested

Tested on windows

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[rajivshah3]

I'm not sure if this is specific to macOS, but for some reason keydown is not fired when caps lock is turned off (instead I think keyup is fired). As a result, the caps lock warning shows until the next character is pressed, which might be a minor UX issue (not a huge deal though)

[obany]

I have added the handler on keyup as well, both can get the modified state without a problem, so that should catch both cases.