[RELEASE] Notepad++ 6.8.9 release

[RELEASE] Notepad++ 6.8.8 release

[RELEASE] Notepad++ 6.8.7 release

[RELEASE] Notepad++ 6.8.6 release

[RELEASE] Notepad++ 6.8.5 release

[RELEASE] Notepad++ 6.8.4 release

[RELEASE] Notepad++ release 6.8.3

[RELEASE] Notepad++ 6.8.2 release

Use default font if font name loaded from stylers.xml cannot be found in
system.

Update CONTRIBUTING.md

Improve readability of CONTRIBUTING.md (closes notepad-plus-plus#513)