[Process]: Adding makefile (#28)

- Added branch-clean script in make file.
- Added coverage.

makefile

@@ -0,0 +1,10 @@
+.PHONY: coverage
+coverage:
+	echo "Running coverage tests"
+	yarn test -- --coverage --watchAll=false
+	open -a Firefox http://localhost:3000
+	serve -s coverage/lcov-report
+
+.PHONY: branch-clean
+branch-clean:
+	git fetch -p && git branch -vv | awk '/: gone]/{print $1}' | xargs git branch -D