Enable flashFrame usage on linux

[alexcarson440]

Update the function that calls flashFrame when receiving a "Loud" notification so that it will execute on linux, as well as windows. This will flash the window to attract user's attention when there are new unread messages until the window is focused again. This will bring parity for behavior between the Windows and Linux desktop apps.

Fixes: #715
Type: defect

Checklist

• Ensure your code works with manual testing.
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• Sign-off given on the changes (see CONTRIBUTING.md).

[dbkr]

Seems good, I assume the fact this this happens unconditionally on Windows means that we don't need to worry about whether the user has such features enabled or not? I also wonder why we need to explicitly check for the OS rather than just doing it anyway and it being a no-op if it's not supported.

[alexcarson440]

Seems good, I assume the fact this this happens unconditionally on Windows means that we don't need to worry about whether the user has such features enabled or not? I also wonder why we need to explicitly check for the OS rather than just doing it anyway and it being a no-op if it's not supported.

To be honest, I agree with this, I think there is no reason it shouldn't be called regardless of OS, but I was just following the existing logic. I can do another PR to take the OS check out if that's wanted.

I also think that there could be a setting added for this (as requested in #743), but that would take a bit more work to implement that the quick fix here.