The module field in package.json should point to src/index.mjs

Also rename the UMD dist file to /index.js.

.gitignore

@@ -1,3 +1,3 @@
 node_modules
-cached-iterable.js
+index.js
 compat.js

Makefile

@@ -22,9 +22,9 @@ test:
 	    --require mocha_config \
 	    test/**/*_test.js
 
-build: $(PACKAGE).js compat.js
+build: index.js compat.js
 
-$(PACKAGE).js: $(SOURCES)
+index.js: $(SOURCES)
 	@rollup $(CURDIR)/src/index.mjs \
 	    --config $(CURDIR)/bundle_config.js \
 	    --banner "/* $(PACKAGE)@$(VERSION) */" \
@@ -43,5 +43,5 @@ compat.js: $(SOURCES)
 	@echo -e " $(OK) $@ built"
 
 clean:
-	@rm -f $(PACKAGE).js compat.js
+	@rm -f index.js compat.js
 	@echo -e " $(OK) clean"

package.json

@@ -17,8 +17,8 @@
   "directories": {
     "lib": "./src"
   },
-  "main": "./cached-iterable.js",
-  "module": "./src/index.js",
+  "main": "./index.js",
+  "module": "./src/index.mjs",
   "repository": {
     "type": "git",
     "url": "https://github.com/projectfluent/cached-iterable.git"