feat: add unit type

Author: pengzhanbo

src/types/index.d.ts

@@ -0,0 +1,6 @@
+export * from './property'
+export * from './unit'
+export * from './at-rule'
+export * from './media'
+export * from './selector'
+export * from './functions'

src/types/unit.d.ts

@@ -0,0 +1,17 @@
+export type RelativeUnit = 'em' | 'rem' | 'vw' | 'vh' | 'vmin' | 'vmax' | 'ex' | 'cap' | 'ch' | 'ic' | 'lh' | 'rlh' | 'vi' | 'vb'
+
+export type AbsoluteUnit = 'px' | 'pt' | 'cm' | 'mm' | 'Q' | 'in' | 'pc'
+
+export type AngleUnit = 'deg' | 'grad' | 'rad' | 'turn'
+
+export type PercentUnit = '%'
+
+export type TimeUnit = 'ms' | 's'
+
+export type FrequencyUnit = 'Hz' | 'kHz'
+
+export type ResolutionUnit = 'dpi' | 'dpcm' | 'dppx'
+
+export type CustomUnit = 'rpx'
+
+export type Unit = RelativeUnit | AbsoluteUnit | AngleUnit | PercentUnit | TimeUnit | FrequencyUnit | ResolutionUnit | CustomUnit