ci: move to codecov for report upload platform

Author: heywhy

.github/workflows/test.yml

@@ -25,10 +25,9 @@ jobs:
       - name: Run Tests
         run: |
           mix coveralls.json
-          # mix coveralls.github
       
       - name: Upload Coverage Reports
         run: |
           curl -Os https://uploader.codecov.io/latest/linux/codecov
           chmod +x codecov
-          ./codecov
+          ./codecov --dir ./cover

README.md

@@ -1,6 +1,6 @@
 # Elasticlunr
 
-[![Dialyzer](https://github.com/heywhy/ex_elasticlunr/actions/workflows/dialyzer.yml/badge.svg?branch=master)](https://github.com/heywhy/ex_elasticlunr/actions) [![Test](https://github.com/heywhy/ex_elasticlunr/actions/workflows/test.yml/badge.svg?branch=master)](https://github.com/heywhy/ex_elasticlunr/actions) [![Coverage Status](https://coveralls.io/repos/github/heywhy/ex_elasticlunr/badge.svg)](https://coveralls.io/github/heywhy/ex_elasticlunr)
+[![Dialyzer](https://github.com/heywhy/ex_elasticlunr/actions/workflows/dialyzer.yml/badge.svg?branch=master)](https://github.com/heywhy/ex_elasticlunr/actions) [![Test](https://github.com/heywhy/ex_elasticlunr/actions/workflows/test.yml/badge.svg?branch=master)](https://github.com/heywhy/ex_elasticlunr/actions) [![Codecov](https://codecov.io/gh/heywhy/ex_elasticlunr/branch/master/graph/badge.svg?token=ZDA9GUTAFJ)](https://codecov.io/gh/heywhy/ex_elasticlunr)
 
 Elasticlunr is a small, full-text search library for use in the Elixir environment. It indexes JSON documents and provides a friendly search interface to retrieve documents.