[@types/luxon] Fix and simplify Duration units.

The units that can be passed as keys in a an object for methods like
`plus` are the same unit that can be passed by string in methods like
`as`. And in both cases both singular and plural versions are accepted
as they [get normalized](https://github.com/moment/luxon/blob/5c449fef840f8023e2444cbb3497272078623a2c/src/duration.js#L233).

types/luxon/index.d.ts

@@ -244,7 +244,9 @@ export class DateTime {
     minus(duration: Duration | number | DurationObject): DateTime;
     plus(duration: Duration | number | DurationObject): DateTime;
     reconfigure(properties: LocaleOptions): DateTime;
-    resolvedLocaleOpts(options?: DateTimeFormatOptions): Intl.ResolvedDateTimeFormatOptions;
+    resolvedLocaleOpts(
+        options?: DateTimeFormatOptions
+    ): Intl.ResolvedDateTimeFormatOptions;
     set(values: DateObjectUnits): DateTime;
     setLocale(locale: string): DateTime;
     setZone(zone: string | Zone, options?: ZoneOptions): DateTime;
@@ -283,37 +285,29 @@ export interface DurationOptions {
 }
 
 export interface DurationObjectUnits {
+    year?: number;
     years?: number;
+    quarter?: number;
+    quarters?: number;
+    month?: number;
     months?: number;
+    week?: number;
     weeks?: number;
+    day?: number;
     days?: number;
+    hour?: number;
     hours?: number;
+    minute?: number;
     minutes?: number;
+    second?: number;
     seconds?: number;
+    millisecond?: number;
     milliseconds?: number;
 }
 
 export interface DurationObject extends DurationObjectUnits, DurationOptions {}
 
-export type DurationUnit =
-    | "year"
-    | "years"
-    | "quarter"
-    | "quarters"
-    | "month"
-    | "months"
-    | "week"
-    | "weeks"
-    | "day"
-    | "days"
-    | "hour"
-    | "hours"
-    | "minute"
-    | "minutes"
-    | "second"
-    | "seconds"
-    | "millisecond"
-    | "milliseconds";
+export type DurationUnit = keyof DurationObjectUnits;
 
 export interface DurationToFormatOptions extends DateTimeFormatOptions {
     floor?: boolean;

types/luxon/luxon-tests.ts

@@ -118,6 +118,7 @@ const { input, result, zone } = DateTime.fromFormatExplain('Aug 6 1982', 'MMMM d
 /* Duration */
 const dur = Duration.fromObject({ hours: 2, minutes: 7 });
 dt.plus(dur); // $ExpectType DateTime
+dt.plus({ quarters: 2, month: 1 }); // $ExpectType DateTime
 dur.hours; // $ExpectType number
 dur.minutes; // $ExpectType number
 dur.seconds; // $ExpectType number
@@ -274,7 +275,7 @@ end.diffNow(['months', 'days']); // $ExpectType Duration
 
 dur.as('days'); // $ExpectType number
 dur.shiftTo('days').toObject().days; // $ExpectType number | undefined
-dur.shiftTo('weeks', 'hours').toObject().weeks; // $ExpectType number | undefined
+dur.shiftTo('week', 'hours').toObject().weeks; // $ExpectType number | undefined
 DateTime.local().plus(dur.shiftTo('milliseconds')).year; // $ExpectType number
 
 Duration.fromISO('PY23', { conversionAccuracy: 'longterm' }); // $ExpectType Duration