feat: export isDraftable

For use by Immer-based libraries

src/immer.d.ts

@@ -157,9 +157,12 @@ export function applyPatches<S>(base: S, patches: Patch[]): S
 /** Get the underlying object that is represented by the given draft */
 export function original<T>(value: T): T | void
 
-/** For detecting an Immer draft */
+/** Returns true if the given value is an Immer draft */
 export function isDraft(value: any): boolean
 
+/** Returns true if the given value can be drafted by Immer */
+export function isDraftable(value: any): boolean
+
 export class Immer {
     constructor(config: {
         useProxies?: boolean

src/index.js

@@ -50,6 +50,7 @@ export const applyPatches = produce(applyPatchesImpl)
 export {
     original,
     isDraft,
+    isDraftable,
     NOTHING as nothing,
     DRAFTABLE as immerable
 } from "./common"