Derani diphthong reform

When writing Derani, we could get rid of the diphthong mark (◌󱛎◌), and instead reuse more consonant glyphs to write falling diphthongs. This makes the writing system more compact and reduces the amount of marks underneath vowels.

Official	Reform	Mnemonic
󱚺󱛎󱚹 aı	󱚶   aı / d	"High" spiral
󱚺󱛎󱛃 ao	󱚳   ao / p	󱚺 a with a tail
󱚴󱛎󱚹 eı	󱚸   eı / z	󱚴 e with an 󱚹 ı flourish
󱛃󱛎󱚹 oı	󱚽   oı / nh	"Low" spiral

As a further mnemonic, the a diphthongs are both 9-shaped while the other two are ∂-shaped.