BlightfallHelper optional local fonts

BlightfallHelper automatically detects:
1. WoW's built-in fonts.
2. Fonts registered through LibSharedMedia-3.0 (for example fonts exposed by
   WeakAuras, SharedMedia, or another installed addon).
3. Compatible font files placed in this folder using the filenames below.

Expected optional filenames:
Arial Bold.ttf
Arial Narrow.ttf
Avant Garde Naowh.ttf
Barlow Condensed.ttf
Changa.ttf
Cinzel Decorative.ttf
Exo.otf
Expressway Bold.ttf
Expressway.ttf
FiraSans Bold.ttf
FiraSans Light.ttf
FiraSans Medium.ttf
Future X Black.otf
Gotham Narrow Ultra.ttf
Gotham Narrow.otf
Homespun.ttf
KMT Kimberley.otf
KMT Ninja Naruto.ttf
Poppins.ttf
Russo One.ttf
Ubuntu.ttf

The font picker renders each available font name using that font.
