CI: Update configuration for code coverage uploading to Codecov.io

- Use `cpython` flag
- Fail CI when upload fails
- Add Codecov.io badge to README

Author: amotl

.github/workflows/tests.yml

@@ -70,10 +70,10 @@ jobs:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
           files: ./coverage.xml
-          flags: main
+          flags: cpython
           env_vars: OS,PYTHON
           name: codecov-umbrella
-          fail_ci_if_error: false
+          fail_ci_if_error: true
 
 
   test-micropython:

README.md

@@ -1,6 +1,7 @@
 # micropython-cratedb - A CrateDB Driver for MicroPython
 
 [![Tests](https://github.com/crate/micropython-cratedb/actions/workflows/tests.yml/badge.svg)](https://github.com/crate/micropython-cratedb/actions/workflows/tests.yml)
+[![Test coverage](https://img.shields.io/codecov/c/gh/crate/micropython-cratedb.svg?style=flat-square)](https://codecov.io/gh/crate/micropython-cratedb/)
 
 ## Introduction