Please add Fluent UI icon(s) for toolbar

[pryrt]

As of Notepad++ v8.0, plugin authors need to call NPPM_ADDTOOLBARICON_FORDARKMODE instead of NPPM_ADDTOOLBARICON. (It could be done in an "if", because you can read the NPP version from a plugin; but also, I don't think it hurts to call both messages, so just running both all the time should work as well... though I'm not a plugin developer, so it would be best to confirm that)

Description of the Issue

Missing toolbar icon when Fluent UI icons selected

Steps to Reproduce the Issue

1. Notepad++ v8.0
2. Settings > Preferences > General, select one of the Fluent UI icon sets
3. NppFTP icon disappears from toolbar

Expected Behavior

NppFTP icon should still have icon

Actual Behavior

NppFTP icon disappears from toolbar

Debug Information

Notepad++ v8   (64-bit)
Build time : Jun  6 2021 - 18:38:25
Path : C:\usr\local\apps\notepad++\notepad++.exe
Command Line : 
Admin mode : OFF
Local Conf mode : ON
Cloud Config : OFF
OS Name : Windows 10 Enterprise (64-bit) 
OS Version : 1903
OS Build : 18362.1256
Current ANSI codepage : 1252
Plugins : ComparePlugin.dll ExtSettings.dll HexEditor.dll LuaScript.dll MarkdownViewerPlusPlus.dll mimeTools.dll NppConsole.dll NppConverter.dll NppEditorConfig.dll NppExec.dll NppExport.dll NppFTP.dll NppUISpy.dll PreviewHTML.dll PythonScript.dll QuickText.dll TagLEET.dll XMLTools.dll 

[chcg]

This was also not working with 7.9.5 and before for the small and big icon set but not as obvious as no icon is displayed in the older versions instead of just a empty button with 8.0 and newer.

[chcg]

This was fixed by N++ itself to fallback to existing BMP icon also for dark mode and the fluent icons.