feat: provide internal API through extend namespace

Author: atheck

package.json

@@ -59,8 +59,10 @@
   "exports": {
     ".": "./dist/index.js",
     "./testing": "./dist/testing/index.js",
+    "./extend": "./dist/extend/index.js",
     "./immutable": "./dist/immutable/index.js",
-    "./immutable/testing": "./dist/immutable/testing/index.js"
+    "./immutable/testing": "./dist/immutable/testing/index.js",
+    "./immutable/extend": "./dist/immutable/extend/index.js"
   },
   "types": "dist/index.d.ts"
 }

src/extend/index.ts

@@ -0,0 +1,2 @@
+export { createCallBase } from "../createCallBase";
+export { createDefer } from "../createDefer";

src/immutable/extend/index.ts

@@ -0,0 +1,2 @@
+export { createCallBase } from "../createCallBase";
+export { createDefer } from "../createDefer";