add index.d.ts and declare it in package.json

index.d.ts

@@ -0,0 +1,24 @@
+type CPSFn<
+  Callbacks extends Array<(...args: unknown[]) => void>
+> = (...args: Callbacks) => void
+
+type ChainFns<
+  FromCallbacks extends Array<(...args: unknown[]) => void>,
+  ToCallbacks extends Array<(...args: unknown[]) => void>,
+> = {
+  [T in keyof FromCallbacks]?: (...args: Parameters<FromCallbacks[T]>) => CPSFn<ToCallbacks> | undefined
+}
+
+type CPS<
+  Callbacks extends Array<(...args: unknown[]) => void>
+> = CPSFn<Callbacks> & {
+  chain<
+    ToCallbacks extends Array<(...args: unknown[]) => void>
+  >(...fns: ChainFns<Callbacks, ToCallbacks>): CPS<ToCallbacks>
+}
+
+declare function CPS<
+  Callbacks extends Array<(...args: unknown[]) => void>
+>(fn: CPSFn<Callbacks>): CPS<Callbacks>
+
+export { CPS, CPSFn }

package.json

@@ -3,8 +3,10 @@
   "name": "cpsfy",
   "description": "Tiny goodies for Continuation-Passing-Style functions",
   "main": "index.js",
+  "types": "index.d.ts",
   "files": [
     "index.js",
+    "index.d.ts",
     "utils.js"
   ],
   "repository": "https://github.com/dmitriz/cpsfy.git",