[3.14] gh-137025: Include python.worker.mjs in the Emscripten Web Example (GH-137236) (#137272)

gh-137025: Include ``python.worker.mjs`` in the Emscripten Web Example (GH-137236)
(cherry picked from commit d5191ba)

Co-authored-by: adam j hartz <hz@mit.edu>

Author: miss-islington

Makefile.pre.in

@@ -1109,6 +1109,10 @@ web_example/index.html: $(WEBEX_DIR)/index.html
 	@mkdir -p web_example
 	@cp $< $@
 
+web_example/python.worker.mjs: $(WEBEX_DIR)/python.worker.mjs
+	@mkdir -p web_example
+	@cp $< $@
+
 web_example/server.py: $(WEBEX_DIR)/server.py
 	@mkdir -p web_example
 	@cp $< $@
@@ -1126,7 +1130,7 @@ web_example/python.mjs web_example/python.wasm: $(BUILDPYTHON)
 	cp python.wasm web_example/python.wasm
 
 .PHONY: web_example
-web_example: web_example/python.mjs web_example/index.html web_example/server.py web_example/$(ZIP_STDLIB)
+web_example: web_example/python.mjs web_example/python.worker.mjs web_example/index.html web_example/server.py web_example/$(ZIP_STDLIB)
 
 WEBEX2=web_example_pyrepl_jspi
 WEBEX2_DIR=$(EMSCRIPTEN_DIR)/$(WEBEX2)/