Add & register more basic commands

src/util/types.ts

@@ -3,6 +3,8 @@ export type Awaitable<T> = T | Promise<T>
 export type JSONScalar = string | boolean | number | undefined
 export type JSONData = JSONScalar | Array<JSONScalar | JSONData> | { [key: string]: JSONScalar | JSONData }
 
+export type ElementType<T extends readonly any[]> = T extends (infer U)[] ? U : never;
+
 /** A typescript-compatible version of Object.hasOwnProperty. */
 export function hasOwnProperty<X extends {}, Y extends PropertyKey>(obj: X, prop: Y): obj is X & Record<Y, unknown> {  // eslint-disable-line @typescript-eslint/ban-types
     return Object.hasOwnProperty.call(obj, prop)